public void TestGetPath()
{
var nodes = new Node[10];
for (var i = 0; i < nodes.Length; i++)
{
var node = new Node(i);
nodes[i] = node;
if (i <= 0) continue;
nodes[i - 1].Next = node;
node.Previous = nodes[i - 1];
}
var path = nodes.GetPath();
var res = path.ToList();
Assert.That(res[0], Is.EqualTo(0));
for (var i = 1; i < res.Count; i++)
{
Assert.That(res[i], Is.EqualTo(i));
}
}
private static Node[] CreteNodesAndDistancesForSIngle2Opt(out double[][] distances)
{
var nodes = new Node[4];
for (var i = 0; i < nodes.Length; i++)
{
var node = new Node(i);
nodes[i] = node;
if (i <= 0) continue;
nodes[i - 1].Next = node;
node.Previous = nodes[i - 1];
}
const int a = 0, b = 1, d = 3, c = 2;
distances = new double[nodes.Length][];
distances[a] = new double[nodes.Length];
distances[b] = new double[nodes.Length];
distances[c] = new double[nodes.Length];
distances[d] = new double[nodes.Length];
distances[a][b] = 1;
distances[b][d] = 1;
distances[d][c] = 1;
distances[b][a] = 1;
distances[d][b] = 1;
distances[c][d] = 1;
distances[a][d] = 0.5;
distances[d][a] = 0.5;
distances[b][c] = 0.5;
distances[c][b] = 0.5;
return nodes;
}
public Node(int index, Node previous)
: this(index)
{
Previous = previous;
}
public static void TwoOpt(Node a, Node c, double[][] distances)
{
//if either of seeds is end of path
if (a == null || c == null) return;
if (a.Next == null || c.Next == null) return;
var b = a.Next;
var d = c.Next;
var ab = distances[a.Index][b.Index];
var cd = distances[c.Index][d.Index];
var ad = distances[a.Index][d.Index];
var bc = distances[b.Index][c.Index];
var abcd = ab + cd;
var adbc = ad + bc;
if (adbc > abcd) return;
c.ToggleDirection();
b.Next?.ToggleDirection();
a.Next = c;
c.Next = c.Previous;
c.Previous = a;
b.Previous = b.Next;
b.Next = d;
d.Previous = b;
}
public static void RandomTwoOpt(Node[] path, double[][] distances)
{
var r = new Random(4711);
for (var i = 0; i < 20*Math.Pow(10, 6); i++)
{
var a = path[r.Next(path.Length)];
var c = path[r.Next(path.Length)];
TwoOpt(a, c, distances);
}
}
public static Node[] RandomApprox(int n)
{
var nodes = new Node[n];
var visited = new HashSet<int>();
var r = new Random(4711);
for (var i = 0; i < n; i++)
{
int index;
while (!visited.Add(index = r.Next(n)));
nodes[i] = new Node(index);
if (i <= 0) continue;
nodes[i].Previous = nodes[i - 1];
nodes[i - 1].Next = nodes[i];
}
nodes[0].Previous = nodes.Last();
nodes.Last().Next = nodes[0];
return nodes;
}
public static Node[] Greedy(IReadOnlyCollection<Coordinate> coordinates, double[][] distances)
{
var r = new Random(5);
var current = r.Next(coordinates.Count);
var visited = new HashSet<int>();
var path = new List<Node> {new Node(current)};
while(path.Count < coordinates.Count)
{
var i = current;
var closest = distances[i].SkipIndices(visited).ToList().IndexOfMin();
var closestNode = new Node(i, path.Last());
path.Last().Next = closestNode;
path.Add(closestNode);
current = closest;
visited.Add(i);
}
return path.ToArray();
}
