我正在尝试编写一个小片段来计算通过一系列点的最短路径。
以下是代码：
using System.Collections.Generic;
using System.Linq;
using System;
namespace ConsoleApplication1
{
public class Waypoint
{
public Point P;
public bool Visited;
}
public class Point
{
public double X;
public double Y;
public Point(double x, double y)
{
this.X = x;
this.Y = y;
}
class Program
{
static List<Point> AllPoints = new List<Point>();
static Point startPoint = new Point(0, 0);
static Point endPoint = new Point(4, 3);
static List<List<Waypoint>> weightedList = new List<List<Waypoint>>();
static void Main(string[] args)
{
AllPoints.Add(new Point(0, 0));
AllPoints.Add(new Point(1, 1));
AllPoints.Add(new Point(1, 2));
AllPoints.Add(new Point(1, 3));
AllPoints.Add(new Point(2, 2));
AllPoints.Add(new Point(2, 3));
AllPoints.Add(new Point(3, 2));
AllPoints.Add(new Point(3, 3));
AllPoints.Add(new Point(4, 3));
// select all points within reach, its a 1x1 square between points so the max distance is 1.42
var filteredList = from p in AllPoints
where DistanceBetweenTwoPoints(p, startPoint) < 1.42 && p.X != startPoint.X && p.Y != startPoint.Y
select p;
List<Waypoint> currList = new List<Waypoint>();
currList.Add(new Waypoint() { P = new Point(startPoint.X, startPoint.Y), Visited = true });
foreach (var p in filteredList)
{
currList.Add(new Waypoint() { P = new Point(p.X, p.Y), Visited = true });
RecusivlyVisitPoint(currList[currList.Count-1], currList);
}
}
static void RecusivlyVisitPoint(Waypoint wp, List<Waypoint> list)
{
// we have reached the end
if (wp.P == endPoint)
{
weightedList.Add(list);
return;
}
// select all points within reach, its a 1x1 square between points so the max distance is 1.42
List<Point> allPointsWithInReach = (from p in AllPoints
where DistanceBetweenTwoPoints(p, wp.P) < 1.42
select p).ToList<Point>();
// filter with already visited
for (int k = allPointsWithInReach.Count<Point>()-1; k >= 0; k--)
{
Point p = allPointsWithInReach[k];
foreach (var lP in list)
if (lP.P == p)
allPointsWithInReach.RemoveAt(k);
}
// there are no other points to go thru
if (allPointsWithInReach.Count == 0)
{
weightedList.Add(list);
return;
}
// recursivly go thru the list
foreach (var p in allPointsWithInReach)
{
List<Waypoint> newList = new List<Waypoint>();
foreach (var e in list)
newList.Add(e);
newList.Add(new Waypoint() { P = new Point(p.X, p.Y), Visited = true });
RecusivlyVisitPoint(newList[newList.Count - 1], newList);
}
}
static double DistanceBetweenTwoPoints(Point p1, Point p2)
{
return Math.Sqrt(Math.Pow(Math.Abs(p1.X - p2.X), 2) + Math.Pow(Math.Abs(p1.Y - p2.Y), 2));
}
}
}
这是一个1x1“网格”，因此您可以看到我从当前站立点过滤了可能的点距离1.42但尚未访问过。
这里的问题是它通过所有点运行，返回if (wp.P == endPoint)处的所有点。我错过了什么？我创建了一个新列表，并在每个节点的递归中进一步发送它。
最后，没有实现，我将总结weightedList中每个列表中的所有列表项，并选择具有最少元素的列表项。
答案 0 :(得分：0)
首先，当我尝试运行您的代码时，我看到了这段代码：
for (int k = allPointsWithInReach.Count<Point>()-1; k >= 0; k--)
{
Point p = allPointsWithInReach[k];
foreach (var lP in list)
if (lP.P == p)
allPointsWithInReach.RemoveAt(k);
}
没有删除您已经去过的任何一点。这意味着它进入了一个无限循环并创建了一个stackoverflow异常。
我删除了你用linq去的点更简洁。为了做到这一点，我需要评估2点是否等于所以我在点类中添加了2个方法。 这是代码：
using System.Collections.Generic;
using System.Linq;
using System;
namespace ConsoleApplication1
{
public class Waypoint
{
public Point P;
public bool Visited;
}
public class Point : IEquatable<Point>
{
public double X;
public double Y;
public Point(double x, double y)
{
this.X = x;
this.Y = y;
}
public bool Equals(Point other)
{
if (Object.ReferenceEquals(other, null)) return false;
if (Object.ReferenceEquals(this, other)) return true;
return X.Equals(other.X) && Y.Equals(other.Y);
}
public override int GetHashCode()
{
int hashX = X.GetHashCode();
int hashY = Y.GetHashCode();
return hashX ^ hashY;
}
}
class Program
{
static List<Point> AllPoints = new List<Point>();
static Point startPoint = new Point(0, 0);
static Point endPoint = new Point(4, 3);
static List<List<Waypoint>> weightedList = new List<List<Waypoint>>();
static void Main(string[] args)
{
AllPoints.Add(new Point(0, 0));
AllPoints.Add(new Point(1, 1));
AllPoints.Add(new Point(1, 2));
AllPoints.Add(new Point(1, 3));
AllPoints.Add(new Point(2, 2));
AllPoints.Add(new Point(2, 3));
AllPoints.Add(new Point(3, 2));
AllPoints.Add(new Point(3, 3));
AllPoints.Add(new Point(4, 3));
// select all points within reach, its a 1x1 square between points so the max distance is 1.42
var filteredList = from p in AllPoints
where DistanceBetweenTwoPoints(p, startPoint) < 1.42 && p.X != startPoint.X && p.Y != startPoint.Y
select p;
List<Waypoint> currList = new List<Waypoint>();
currList.Add(new Waypoint() { P = new Point(startPoint.X, startPoint.Y), Visited = true });
foreach (var p in filteredList)
{
currList.Add(new Waypoint() { P = new Point(p.X, p.Y), Visited = true });
RecusivlyVisitPoint(currList.Last(), currList);
}
var min = weightedList.OrderBy(w => w.Count).Take(1).ToList();
}
static void RecusivlyVisitPoint(Waypoint wp, List<Waypoint> list)
{
// we have reached the end
if (wp.P.Equals(endPoint))
{
weightedList.Add(list);
return;
}
// select all points within reach, its a 1x1 square between points so the max distance is 1.42
var allPointsWithInReach = AllPoints.FindAll(p => DistanceBetweenTwoPoints(p, wp.P) < 1.42);
// filter with already visited
allPointsWithInReach = allPointsWithInReach.Except(list.Select(w => w.P)).ToList();
// there are no other points to go thru
if (allPointsWithInReach.Count == 0)
{
//weightedList.Add(list);
// but you didn't get trough the end so it's not a possibility
return;
}
// recursivly go thru the list
foreach (var p in allPointsWithInReach)
{
List<Waypoint> newList = new List<Waypoint>();
foreach (var e in list)
newList.Add(e);
newList.Add(new Waypoint() { P = new Point(p.X, p.Y), Visited = true });
RecusivlyVisitPoint(newList.Last(), newList);
}
}
static double DistanceBetweenTwoPoints(Point p1, Point p2)
{
return Math.Sqrt(Math.Pow(Math.Abs(p1.X - p2.X), 2) + Math.Pow(Math.Abs(p1.Y - p2.Y), 2));
}
}
}