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source: branches/2895_PushGP_GenealogyAnalysis/HeuristicLab.Problems.ProgramSynthesis/Push.Base/Extensions/StringExtensions.cs @ 17511

Last change on this file since 17511 was 15771, checked in by bburlacu, 7 years ago

#2895: Add solution skeleton for PushGP with genealogy analysis.

File size: 2.6 KB
RevLine 
[15334]1using System;
2
[15771]3namespace HeuristicLab.Problems.ProgramSynthesis {
[15334]4  public static class StringExtensions {
5    public static bool IsNumeric(this string str) {
6      int n;
[15341]7      return int.TryParse(str, out n);
[15334]8    }
9
10    /// <summary>
[15341]11    /// https://github.com/DanHarltey/Fastenshtein
12    /// </summary>
13    public static int LevenshteinDistance(this string source, string target) {
14      if (target.Length == 0) {
15        return source.Length;
16      }
17
18      int[] costs = new int[target.Length];
19
20      // Add indexing for insertion to first row
21      for (int i = 0; i < costs.Length;) {
22        costs[i] = ++i;
23      }
24
25      for (int i = 0; i < source.Length; i++) {
26        // cost of the first index
27        int cost = i;
28        int addationCost = i;
29
30        // cache value for inner loop to avoid index lookup and bonds checking, profiled this is quicker
31        char value1Char = source[i];
32
33        for (int j = 0; j < target.Length; j++) {
34          int insertionCost = cost;
35
36          cost = addationCost;
37
38          // assigning this here reduces the array reads we do, improvement of the old version
39          addationCost = costs[j];
40
41          if (value1Char != target[j]) {
42            if (insertionCost < cost) {
43              cost = insertionCost;
44            }
45
46            if (addationCost < cost) {
47              cost = addationCost;
48            }
49
50            ++cost;
51          }
52
53          costs[j] = cost;
54        }
55      }
56
57      return costs[costs.Length - 1];
58    }
59
60    /// <summary>
[15334]61    /// https://www.dotnetperls.com/levenshtein
62    /// </summary>
[15341]63    public static int LevenshteinDistance2(this string source, string target) {
[15334]64      if (source == null && target == null) return 0;
65      if (source == null) return target.Length;
66      if (target == null) return source.Length;
67
68      int n = source.Length;
69      int m = target.Length;
70      int[,] d = new int[n + 1, m + 1];
71
72      // Step 1
73      if (n == 0) {
74        return m;
75      }
76
77      if (m == 0) {
78        return n;
79      }
80
81      // Step 2
82      for (int i = 0; i <= n; d[i, 0] = i++) {
83      }
84
85      for (int j = 0; j <= m; d[0, j] = j++) {
86      }
87
88      // Step 3
89      for (int i = 1; i <= n; i++) {
90        //Step 4
91        for (int j = 1; j <= m; j++) {
92          // Step 5
93          int cost = (target[j - 1] == source[i - 1]) ? 0 : 1;
94
95          // Step 6
96          d[i, j] = Math.Min(
97              Math.Min(d[i - 1, j] + 1, d[i, j - 1] + 1),
98              d[i - 1, j - 1] + cost);
99        }
100      }
101      // Step 7
102      return d[n, m];
103    }
104  }
105}
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