public static void Disturb(Path path, int k = 3)
{
for (int i = 0; i < k; i++)
{
var edgesForSwapping = FindEdgesForSwapping(path, 2);
PathEditorHelper.RemoveOldEdges(edgesForSwapping, path);
var newEdges = SwapEdges(edgesForSwapping);
PathEditorHelper.AddNewEdges(newEdges, path);
}
}
public static bool _2OPT(Path path)
{
// take first edge that has possibility to be swapped
for (int firstEdgeIndex = 0; firstEdgeIndex < edgesCount - 3; ++firstEdgeIndex)
{
// take first non-neighbour edge corresponding to firstEdgeIndex
for (int secondEdgeIndex = firstEdgeIndex + 2; secondEdgeIndex < edgesCount - 1; ++secondEdgeIndex)
{
var firstEdge = allEdges[firstEdgeIndex];
var secondEdge = allEdges[secondEdgeIndex];
var firstEdgeLength = citiesDictionary[firstEdge.FromCityId].Connections[firstEdge.ToCityId];
var secondEdgeLength = citiesDictionary[secondEdge.FromCityId].Connections[secondEdge.ToCityId];
var oldLength = firstEdgeLength + secondEdgeLength;
var newFirstEdgeLength = citiesDictionary[firstEdge.FromCityId].Connections[secondEdge.FromCityId];
var newSecondEdgeLength = citiesDictionary[firstEdge.ToCityId].Connections[secondEdge.ToCityId];
var newLength = newFirstEdgeLength + newSecondEdgeLength;
if (newLength < oldLength)
{
var newFirstEdge = new Edge {
FromCityId = firstEdge.FromCityId, ToCityId = secondEdge.FromCityId
};
var newSecondEdge = new Edge {
FromCityId = firstEdge.ToCityId, ToCityId = secondEdge.ToCityId
};
PathEditorHelper.RemoveOldEdges(new List <Edge> {
firstEdge, secondEdge
}, path);
PathEditorHelper.AddNewEdges(new List <Edge> {
newFirstEdge, newSecondEdge
}, path);
allEdges.Remove(firstEdge);
allEdges.Remove(secondEdge);
allEdges.Insert(firstEdgeIndex, newFirstEdge);
allEdges.Insert(secondEdgeIndex, newSecondEdge);
// take all edges between the new ones
var edgesToReverse = allEdges.GetRange(firstEdgeIndex + 1, secondEdgeIndex - firstEdgeIndex - 1);
// reverse edges taken above
var reversedEdges = new List <Edge>();
foreach (var edge in edgesToReverse)
{
reversedEdges.Add(new Edge {
FromCityId = edge.ToCityId, ToCityId = edge.FromCityId
});
}
reversedEdges.Reverse();
allEdges.RemoveRange(firstEdgeIndex + 1, secondEdgeIndex - firstEdgeIndex - 1);
allEdges.InsertRange(firstEdgeIndex + 1, reversedEdges);
return(true);
}
}
}
return(false);
}