1 | //******************************
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2 | // Written by Peter Golde
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3 | // Copyright (connector) 2004-2005, Wintellect
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4 | //
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5 | // Use and restribution of this code is subject to the license agreement
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6 | // contained in the file "License.txt" accompanying this file.
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7 | //******************************
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8 |
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9 | using System;
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10 | using System.Collections;
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11 | using System.Collections.Generic;
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12 |
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13 | #pragma warning disable 419 // Ambigious cref in XML comment
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14 |
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15 | namespace Netron.Diagramming.Core
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16 | {
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17 |
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18 | /// <summary>
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19 | /// Algorithms contains a number of static methods that implement
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20 | /// algorithms that work on collections. Most of the methods deal with
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21 | /// the standard generic collection interfaces such as IEnumerable<T>,
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22 | /// ICollection<T> and IList<T>.
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23 | /// </summary>
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24 | public static class Algorithms
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25 | {
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26 |
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27 | /// <summary>
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28 | /// Create an IEnumerable that enumerates an array. Make sure that only enumerable stuff
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29 | /// is used and no downcasts to ICollection are taken advantage of.
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30 | /// </summary>
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31 | /// <param name="array">An array.</param>
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32 | /// <returns>An IEnumerable cast of the array</returns>
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33 | /// <typeparam name="T">a </typeparam>
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34 | /// <example>The following code
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35 | /// <code>
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36 | ///
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37 | /// </code>
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38 | /// </example>
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39 | public static IEnumerable<T> EnumerableFromArray<T>(T[] array)
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40 | {
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41 | foreach (T t in array)
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42 | yield return t;
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43 | }
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44 |
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45 |
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46 |
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47 | #region String representations
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48 |
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49 | /// <summary>
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50 | /// Gets a string representation of the elements in the collection.
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51 | /// The string representation starts with "{", has a list of items separated
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52 | /// by commas (","), and ends with "}". Each item in the collection is
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53 | /// converted to a string by calling its ToString method (null is represented by "null").
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54 | /// Contained collections (except strings) are recursively converted to strings by this method.
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55 | /// </summary>
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56 | /// <param name="collection">A collection to get the string representation of.</param>
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57 | /// <returns>The string representation of the collection. If <paramref name="collection"/> is null, then the string "null" is returned.</returns>
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58 | internal static string ToString<T>(IEnumerable<T> collection)
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59 | {
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60 | return collection.GetType().Name;// ToString(collection);
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61 | }
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62 |
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63 |
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64 |
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65 | /// <summary>
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66 | /// Gets a string representation of the mappings in a dictionary.
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67 | /// The string representation starts with "{", has a list of mappings separated
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68 | /// by commas (", "), and ends with "}". Each mapping is represented
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69 | /// by "key->value". Each key and value in the dictionary is
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70 | /// converted to a string by calling its ToString method (null is represented by "null").
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71 | /// Contained collections (except strings) are recursively converted to strings by this method.
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72 | /// </summary>
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73 | /// <param name="dictionary">A dictionary to get the string representation of.</param>
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74 | /// <returns>The string representation of the collection, or "null"
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75 | /// if <paramref name="dictionary"/> is null.</returns>
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76 | internal static string ToString<TKey, TValue>(IDictionary<TKey, TValue> dictionary)
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77 | {
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78 | bool firstItem = true;
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79 |
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80 | if (dictionary == null)
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81 | return "null";
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82 |
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83 | System.Text.StringBuilder builder = new System.Text.StringBuilder();
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84 |
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85 | builder.Append("{");
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86 |
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87 | // Call ToString on each item and put it in.
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88 | foreach (KeyValuePair<TKey, TValue> pair in dictionary) {
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89 | if (!firstItem)
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90 | builder.Append(", ");
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91 |
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92 | if (pair.Key == null)
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93 | builder.Append("null");
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94 |
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95 | else
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96 | builder.Append(pair.Key.ToString());
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97 |
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98 | builder.Append("->");
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99 |
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100 | if (pair.Value == null)
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101 | builder.Append("null");
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102 |
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103 | else
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104 | builder.Append(pair.Value.ToString());
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105 |
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106 |
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107 | firstItem = false;
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108 | }
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109 |
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110 | builder.Append("}");
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111 | return builder.ToString();
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112 | }
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113 |
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114 | #endregion String representations
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115 |
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116 |
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117 |
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118 |
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119 |
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120 |
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121 |
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122 | #region Predicate operations
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123 |
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124 | /// <summary>
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125 | /// Determines if a collection contains any item that satisfies the condition
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126 | /// defined by <paramref name="predicate"/>.
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127 | /// </summary>
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128 | /// <param name="collection">The collection to check all the items in.</param>
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129 | /// <param name="predicate">A delegate that defines the condition to check for.</param>
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130 | /// <returns>True if the collection contains one or more items that satisfy the condition
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131 | /// defined by <paramref name="predicate"/>. False if the collection does not contain
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132 | /// an item that satisfies <paramref name="predicate"/>.</returns>
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133 | internal static bool Exists<T>(IEnumerable<T> collection, Predicate<T> predicate)
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134 | {
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135 | if (collection == null)
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136 | throw new ArgumentNullException("collection");
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137 | if (predicate == null)
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138 | throw new ArgumentNullException("predicate");
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139 |
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140 | foreach (T item in collection) {
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141 | if (predicate(item))
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142 | return true;
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143 | }
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144 |
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145 | return false;
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146 | }
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147 |
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148 | /// <summary>
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149 | /// Determines if all of the items in the collection satisfy the condition
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150 | /// defined by <paramref name="predicate"/>.
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151 | /// </summary>
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152 | /// <param name="collection">The collection to check all the items in.</param>
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153 | /// <param name="predicate">A delegate that defines the condition to check for.</param>
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154 | /// <returns>True if all of the items in the collection satisfy the condition
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155 | /// defined by <paramref name="predicate"/>, or if the collection is empty. False if one or more items
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156 | /// in the collection do not satisfy <paramref name="predicate"/>.</returns>
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157 | internal static bool TrueForAll<T>(IEnumerable<T> collection, Predicate<T> predicate)
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158 | {
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159 | if (collection == null)
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160 | throw new ArgumentNullException("collection");
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161 | if (predicate == null)
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162 | throw new ArgumentNullException("predicate");
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163 |
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164 | foreach (T item in collection) {
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165 | if (!predicate(item))
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166 | return false;
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167 | }
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168 |
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169 | return true;
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170 | }
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171 | /*
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172 | /// <summary>
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173 | /// Counts the number of items in the collection that satisfy the condition
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174 | /// defined by <paramref name="predicate"/>.
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175 | /// </summary>
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176 | /// <param name="collection">The collection to count items in.</param>
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177 | /// <param name="predicate">A delegate that defines the condition to check for.</param>
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178 | /// <returns>The number of items in the collection that satisfy <paramref name="predicate"/>.</returns>
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179 | public static int CountWhere<T>(IEnumerable<T> collection, Predicate<T> predicate)
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180 | {
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181 | if (collection == null)
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182 | throw new ArgumentNullException("collection");
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183 | if (predicate == null)
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184 | throw new ArgumentNullException("predicate");
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185 |
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186 | int count = 0;
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187 | foreach (T item in collection)
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188 | {
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189 | if (predicate(item))
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190 | ++count;
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191 | }
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192 |
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193 | return count;
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194 | }
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195 | */
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196 | /// <summary>
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197 | /// Removes all the items in the collection that satisfy the condition
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198 | /// defined by <paramref name="predicate"/>.
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199 | /// </summary>
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200 | /// <remarks>If the collection if an array or implements IList<T>, an efficient algorithm that
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201 | /// compacts items is used. If not, then ICollection<T>.Remove is used
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202 | /// to remove items from the collection. If the collection is an array or fixed-size list,
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203 | /// the non-removed elements are placed, in order, at the beginning of
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204 | /// the list, and the remaining list items are filled with a default value (0 or null).</remarks>
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205 | /// <param name="collection">The collection to check all the items in.</param>
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206 | /// <param name="predicate">A delegate that defines the condition to check for.</param>
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207 | /// <returns>Returns a collection of the items that were removed. This collection contains the
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208 | /// items in the same order that they orginally appeared in <paramref name="collection"/>.</returns>
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209 | [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1800:DoNotCastUnnecessarily")]
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210 | internal static ICollection<T> RemoveWhere<T>(ICollection<T> collection, Predicate<T> predicate)
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211 | {
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212 | if (collection == null)
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213 | throw new ArgumentNullException("collection");
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214 | if (predicate == null)
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215 | throw new ArgumentNullException("predicate");
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216 |
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217 |
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218 | IList<T> list = collection as IList<T>;
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219 | if (list != null) {
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220 | T item;
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221 | int i = -1, j = 0;
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222 | int listCount = list.Count;
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223 | List<T> removed = new List<T>();
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224 |
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225 | // Remove item where predicate is true, compressing items to lower in the list. This is much more
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226 | // efficient than the naive algorithm that uses IList<T>.Remove().
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227 | while (j < listCount) {
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228 | item = list[j];
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229 | if (predicate(item)) {
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230 | removed.Add(item);
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231 | }
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232 | else {
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233 | ++i;
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234 | if (i != j)
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235 | list[i] = item;
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236 | }
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237 | ++j;
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238 | }
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239 |
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240 | ++i;
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241 | if (i < listCount) {
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242 | // remove items from the end.
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243 | if (list is IList && ((IList)list).IsFixedSize) {
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244 | // An array or similar. Null out the last elements.
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245 | while (i < listCount)
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246 | list[i++] = default(T);
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247 | }
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248 | else {
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249 | // Normal list.
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250 | while (i < listCount) {
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251 | list.RemoveAt(listCount - 1);
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252 | --listCount;
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253 | }
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254 | }
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255 | }
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256 |
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257 | return removed;
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258 | }
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259 | else {
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260 | // We have to copy all the items to remove to a List, because collections can't be modifed
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261 | // during an enumeration.
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262 | List<T> removed = new List<T>();
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263 |
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264 | foreach (T item in collection)
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265 | if (predicate(item))
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266 | removed.Add(item);
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267 |
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268 | foreach (T item in removed)
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269 | collection.Remove(item);
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270 |
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271 | return removed;
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272 | }
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273 | }
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274 | /*
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275 | /// <summary>
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276 | /// Convert a collection of items by applying a delegate to each item in the collection. The resulting collection
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277 | /// contains the result of applying <paramref name="converter"/> to each item in <paramref name="sourceCollection"/>, in
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278 | /// order.
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279 | /// </summary>
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280 | /// <typeparam name="TSource">The type of items in the collection to convert.</typeparam>
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281 | /// <typeparam name="TDest">The type each item is being converted to.</typeparam>
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282 | /// <param name="sourceCollection">The collection of item being converted.</param>
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283 | /// <param name="converter">A delegate to the method to call, passing each item in <paramref name="sourceCollection"/>.</param>
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284 | /// <returns>The resulting collection from applying <paramref name="converter"/> to each item in <paramref name="sourceCollection"/>, in
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285 | /// order.</returns>
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286 | /// <exception cref="ArgumentNullException"><paramref name="sourceCollection"/> or <paramref name="converter"/> is null.</exception>
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287 | public static IEnumerable<TDest> Convert<TSource, TDest>(IEnumerable<TSource> sourceCollection, Converter<TSource, TDest> converter)
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288 | {
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289 | if (sourceCollection == null)
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290 | throw new ArgumentNullException("sourceCollection");
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291 | if (converter == null)
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292 | throw new ArgumentNullException("converter");
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293 |
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294 | foreach (TSource sourceItem in sourceCollection)
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295 | yield return converter(sourceItem);
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296 | }
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297 | */
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298 | /// <summary>
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299 | /// Creates a delegate that converts keys to values by used a dictionary to map values. Keys
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300 | /// that a not present in the dictionary are converted to the default value (zero or null).
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301 | /// </summary>
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302 | /// <remarks>This delegate can be used as a parameter in Convert or ConvertAll methods to convert
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303 | /// entire collections.</remarks>
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304 | /// <param name="dictionary">The dictionary used to perform the conversion.</param>
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305 | /// <returns>A delegate to a method that converts keys to values. </returns>
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306 | internal static Converter<TKey, TValue> GetDictionaryConverter<TKey, TValue>(IDictionary<TKey, TValue> dictionary)
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307 | {
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308 | return GetDictionaryConverter(dictionary, default(TValue));
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309 | }
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310 |
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311 | /// <summary>
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312 | /// Creates a delegate that converts keys to values by used a dictionary to map values. Keys
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313 | /// that a not present in the dictionary are converted to a supplied default value.
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314 | /// </summary>
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315 | /// <remarks>This delegate can be used as a parameter in Convert or ConvertAll methods to convert
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316 | /// entire collections.</remarks>
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317 | /// <param name="dictionary">The dictionary used to perform the conversion.</param>
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318 | /// <param name="defaultValue">The result of the conversion for keys that are not present in the dictionary.</param>
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319 | /// <returns>A delegate to a method that converts keys to values. </returns>
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320 | /// <exception cref="ArgumentNullException"><paramref name="dictionary"/> is null.</exception>
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321 | internal static Converter<TKey, TValue> GetDictionaryConverter<TKey, TValue>(IDictionary<TKey, TValue> dictionary, TValue defaultValue)
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322 | {
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323 | if (dictionary == null)
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324 | throw new ArgumentNullException("dictionary");
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325 |
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326 | return delegate(TKey key) {
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327 | TValue value;
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328 | if (dictionary.TryGetValue(key, out value))
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329 | return value;
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330 | else
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331 | return defaultValue;
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332 | };
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333 | }
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334 |
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335 | /// <summary>
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336 | /// Performs the specified action on each item in a collection.
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337 | /// </summary>
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338 | /// <param name="collection">The collection to process.</param>
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339 | /// <param name="action">An Action delegate which is invoked for each item in <paramref name="collection"/>.</param>
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340 | internal static void ForEach<T>(IEnumerable<T> collection, Action<T> action)
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341 | {
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342 | if (collection == null)
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343 | throw new ArgumentNullException("collection");
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344 | if (action == null)
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345 | throw new ArgumentNullException("action");
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346 |
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347 | foreach (T item in collection)
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348 | action(item);
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349 | }
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350 |
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351 |
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352 | #endregion Predicate operations
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353 |
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354 |
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355 |
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356 | #region Sorting
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357 | /// <summary>
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358 | /// Sorts a list or array in place.
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359 | /// </summary>
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360 | /// <remarks><para>The Quicksort algorithms is used to sort the items. In virtually all cases,
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361 | /// this takes time O(N log N), where N is the number of items in the list.</para>
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362 | /// <para>Values are compared by using the IComparable<T>
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363 | /// interfaces implementation on the type T.</para>
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364 | /// <para>Although arrays cast to IList<T> are normally read-only, this method
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365 | /// will work correctly and modify an array passed as <paramref name="list"/>.</para></remarks>
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366 | /// <param name="list">The list or array to sort.</param>
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367 | public static void SortInPlace<T>(IList<T> list)
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368 | where T : IComparable<T>
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369 | {
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370 | SortInPlace<T>(list, Comparer<T>.Default);
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371 | }
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372 |
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373 | /// <summary>
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374 | /// Sorts a list or array in place. A supplied IComparer<T> is used
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375 | /// to compare the items in the list.
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376 | /// </summary>
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377 | /// <remarks><para>The Quicksort algorithms is used to sort the items. In virtually all cases,
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378 | /// this takes time O(N log N), where N is the number of items in the list.</para>
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379 | /// <para>Although arrays cast to IList<T> are normally read-only, this method
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380 | /// will work correctly and modify an array passed as <paramref name="list"/>.</para></remarks>
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381 | /// <param name="list">The list or array to sort.</param>
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382 | /// <param name="comparer">The comparer instance used to compare items in the collection. Only
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383 | /// the Compare method is used.</param>
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384 | public static void SortInPlace<T>(IList<T> list, IComparer<T> comparer)
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385 | {
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386 | if(list == null)
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387 | throw new ArgumentNullException("Cannot sort a 'null' list.");
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388 | if(comparer == null)
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389 | throw new ArgumentNullException("The comparer is 'null'.");
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390 |
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391 | // If we have an array, use the built-in array sort (faster than going through IList accessors
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392 | // with virtual calls).
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393 | if(list is T[])
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394 | {
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395 | Array.Sort((T[]) list, comparer);
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396 | return;
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397 | }
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398 |
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399 | if(list.IsReadOnly)
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400 | throw new ArgumentException("The list is readonly.", "list");
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401 |
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402 | // Instead of a recursive procedure, we use an explicit stack to hold
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403 | // ranges that we still need to sort.
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404 | int[] leftStack = new int[32], rightStack = new int[32];
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405 | int stackPtr = 0;
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406 |
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407 | int l = 0; // the inclusive left edge of the current range we are sorting.
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408 | int r = list.Count - 1; // the inclusive right edge of the current range we are sorting.
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409 | T partition; // The partition value.
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410 |
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411 | // Loop until we have nothing left to sort. On each iteration, l and r contains the bounds
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412 | // of something to sort (unless r <= l), and leftStack/rightStack have a stack of unsorted
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413 | // pieces (unles stackPtr == 0).
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414 | for(; ; )
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415 | {
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416 | if(l == r - 1)
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417 | {
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418 | // We have exactly 2 elements to sort. Compare them and swap if needed.
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419 | T e1, e2;
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420 | e1 = list[l];
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421 | e2 = list[r];
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422 | if(comparer.Compare(e1, e2) > 0)
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423 | {
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424 | list[r] = e1;
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425 | list[l] = e2;
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426 | }
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427 | l = r; // sort complete, find other work from the stack.
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428 | }
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429 | else if(l < r)
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430 | {
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431 | // Sort the items in the inclusive range l .. r
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432 |
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433 | // Get the left, middle, and right-most elements and sort them, yielding e1=smallest, e2=median, e3=largest
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434 | int m = l + (r - l) / 2;
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435 | T e1 = list[l], e2 = list[m], e3 = list[r], temp;
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436 | if(comparer.Compare(e1, e2) > 0)
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437 | {
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438 | temp = e1;
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439 | e1 = e2;
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440 | e2 = temp;
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441 | }
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442 | if(comparer.Compare(e1, e3) > 0)
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443 | {
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444 | temp = e3;
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445 | e3 = e2;
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446 | e2 = e1;
|
---|
447 | e1 = temp;
|
---|
448 | }
|
---|
449 | else if(comparer.Compare(e2, e3) > 0)
|
---|
450 | {
|
---|
451 | temp = e2;
|
---|
452 | e2 = e3;
|
---|
453 | e3 = temp;
|
---|
454 | }
|
---|
455 |
|
---|
456 | if(l == r - 2)
|
---|
457 | {
|
---|
458 | // We have exactly 3 elements to sort, and we've done that. Store back and we're done.
|
---|
459 | list[l] = e1;
|
---|
460 | list[m] = e2;
|
---|
461 | list[r] = e3;
|
---|
462 | l = r; // sort complete, find other work from the stack.
|
---|
463 | }
|
---|
464 | else
|
---|
465 | {
|
---|
466 | // Put the smallest at the left, largest in the middle, and the median at the right (which is the partitioning value)
|
---|
467 | list[l] = e1;
|
---|
468 | list[m] = e3;
|
---|
469 | list[r] = partition = e2;
|
---|
470 |
|
---|
471 | // Partition into three parts, items <= partition, items == partition, and items >= partition
|
---|
472 | int i = l, j = r;
|
---|
473 | T item_i, item_j;
|
---|
474 | for(; ; )
|
---|
475 | {
|
---|
476 | do
|
---|
477 | {
|
---|
478 | ++i;
|
---|
479 | item_i = list[i];
|
---|
480 | } while(comparer.Compare(item_i, partition) < 0);
|
---|
481 |
|
---|
482 | do
|
---|
483 | {
|
---|
484 | --j;
|
---|
485 | item_j = list[j];
|
---|
486 | } while(comparer.Compare(item_j, partition) > 0);
|
---|
487 |
|
---|
488 | if(j < i)
|
---|
489 | break;
|
---|
490 |
|
---|
491 | list[i] = item_j;
|
---|
492 | list[j] = item_i; // swap items to continue the partition.
|
---|
493 | }
|
---|
494 |
|
---|
495 | // Move the partition value into place.
|
---|
496 | list[r] = item_i;
|
---|
497 | list[i] = partition;
|
---|
498 | ++i;
|
---|
499 |
|
---|
500 | // We have partitioned the list.
|
---|
501 | // Items in the inclusive range l .. j are <= partition.
|
---|
502 | // Items in the inclusive range i .. r are >= partition.
|
---|
503 | // Items in the inclusive range j+1 .. i - 1 are == partition (and in the correct final position).
|
---|
504 | // We now need to sort l .. j and i .. r.
|
---|
505 | // To do this, we stack one of the lists for later processing, and change l and r to the other list.
|
---|
506 | // If we always stack the larger of the two sub-parts, the stack cannot get greater
|
---|
507 | // than log2(Count) in size; i.e., a 32-element stack is enough for the maximum list size.
|
---|
508 | if((j - l) > (r - i))
|
---|
509 | {
|
---|
510 | // The right partition is smaller. Stack the left, and get ready to sort the right.
|
---|
511 | leftStack[stackPtr] = l;
|
---|
512 | rightStack[stackPtr] = j;
|
---|
513 | l = i;
|
---|
514 | }
|
---|
515 | else
|
---|
516 | {
|
---|
517 | // The left partition is smaller. Stack the right, and get ready to sort the left.
|
---|
518 | leftStack[stackPtr] = i;
|
---|
519 | rightStack[stackPtr] = r;
|
---|
520 | r = j;
|
---|
521 | }
|
---|
522 | ++stackPtr;
|
---|
523 | }
|
---|
524 | }
|
---|
525 | else if(stackPtr > 0)
|
---|
526 | {
|
---|
527 | // We have a stacked sub-list to sort. Pop it off and sort it.
|
---|
528 | --stackPtr;
|
---|
529 | l = leftStack[stackPtr];
|
---|
530 | r = rightStack[stackPtr];
|
---|
531 | }
|
---|
532 | else
|
---|
533 | {
|
---|
534 | // We have nothing left to sort.
|
---|
535 | break;
|
---|
536 | }
|
---|
537 | }
|
---|
538 | }
|
---|
539 |
|
---|
540 |
|
---|
541 | #endregion
|
---|
542 |
|
---|
543 | }
|
---|
544 | }
|
---|