#region License Information
/* HeuristicLab
* Copyright (C) 2002-2016 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
*
* This file is part of HeuristicLab.
*
* HeuristicLab is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* HeuristicLab is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with HeuristicLab. If not, see .
*/
#endregion
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using HeuristicLab.PluginInfrastructure;
namespace HeuristicLab.Encodings.PermutationEncoding {
[NonDiscoverableType]
public class PermutationEqualityComparer : EqualityComparer {
public override bool Equals(Permutation x, Permutation y) {
if (x == null && y == null) return true;
if (x == null || y == null) return false;
if (ReferenceEquals(x, y)) return true;
if (x.Length != y.Length) return false;
if (x.PermutationType != y.PermutationType) return false;
switch (x.PermutationType) {
case PermutationTypes.Absolute:
return EqualsAbsolute(x, y);
case PermutationTypes.RelativeDirected:
return EqualsRelative(x, y, true);
case PermutationTypes.RelativeUndirected:
return EqualsRelative(x, y, false);
default:
throw new InvalidOperationException("unknown permutation type");
}
}
private bool EqualsAbsolute(Permutation x, Permutation y) {
return x.SequenceEqual(y);
}
private bool EqualsRelative(Permutation x, Permutation y, bool directed) {
int[] edgesX = CalculateEdgesVector(x);
int[] edgesY = CalculateEdgesVector(y);
for (int i = 0; i < x.Length; i++)
if ((edgesX[i] != edgesY[i]) && (directed || edgesX[edgesY[i]] != i))
return false;
return true;
}
private int[] CalculateEdgesVector(Permutation permutation) {
// transform path representation into adjacency representation
int[] edgesVector = new int[permutation.Length];
for (int i = 0; i < permutation.Length - 1; i++)
edgesVector[permutation[i]] = permutation[i + 1];
edgesVector[permutation[permutation.Length - 1]] = permutation[0];
return edgesVector;
}
public override int GetHashCode(Permutation obj) {
if (obj == null) throw new ArgumentNullException("obj", "PermutationEqualityComparer: Cannot compute hash value of null.");
return GenerateHashString(obj).GetHashCode();
}
private string GenerateHashString(Permutation p) {
StringBuilder sb = new StringBuilder();
if (p.PermutationType == PermutationTypes.Absolute) {
for (int i = 0; i < p.Length; i++)
sb.Append(p[i].ToString() + ";");
} else {
int i = 0;
while (p[i] != 0) i++; // always start at element 0
if (p.PermutationType == PermutationTypes.RelativeDirected) {
for (int j = 0; j < p.Length; j++)
sb.Append(p.GetCircular(i + j).ToString() + ";");
} else {
bool goLeft = p.GetCircular(i - 1) < p.GetCircular(i + 1); // go in direction of the lowest edge so that the total inversion and its original return the same hash code
for (int j = 0; j < p.Length; j++) {
if (goLeft) sb.Append(p.GetCircular(i - j).ToString() + ";");
else sb.Append(p.GetCircular(i + j).ToString() + ";");
}
}
}
return sb.ToString();
}
}
}