回顾A*算法，偶得一源代码，略有瑕疵，改正之，并置于下。
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace AStarOne
8 {
9 class AStar
10 {
11 public const int OBLIQUE = 14;//sqrt(2.0) is 1.414; they have been amplified.
12 public const int STEP = 10;
13 public int[,] AStarArray { get; private set; }
14 List<Point> CloseList; // Close List
15 List<Point> OpenList; // Open List
16
17 public AStar(int [,] aStar)
18 {
19 this.AStarArray = aStar;
20 OpenList = new List<Point>(AStarArray.Length);// Impossible to be bigger than the number of all data
21 CloseList = new List<Point>(AStarArray.Length);
22 }
23
24 /// <summary>
25 /// Find an achievable path from start to end
26 /// </summary>
27 /// <param name="start"></param>
28 /// <param name="end"></param>
29 /// <param name="IsIgnoreCorner">If ignore diagonal spot</param>
30 /// <returns></returns>
31 public Point FindPath(Point start, Point end, bool IsIgnoreCorner)
32 {
33 OpenList.Add(start);
34 while (0 != OpenList.Count)
35 {
36 var tempStart = OpenList.MinPoint();// get the minimum F
37 OpenList.RemoveAt(0);
38 CloseList.Add(tempStart);
39
40 var surroundPoints = GetSurroundPoints(tempStart, IsIgnoreCorner);// Get surrounding points
41 foreach (var point in surroundPoints)
42 {
43 if (OpenList.Exists(point))// If existing in the open list, choose the minimum G between tempStart and point; Update
44 {
45 FoundPoint(tempStart, point);
46 }
47 else
48 {
49 NotFoundPoint(tempStart, end, point);
50 }
51 }
52
53 if (OpenList.Get(end) != null)
54 return OpenList.Get(end);
55 }
56
57 return OpenList.Get(end);
58 }
59
60 private void FoundPoint(Point tempStart, Point point)
61 {
62 var G = CalcG(tempStart, point);
63 if (G < point.G)// the minimum one
64 {
65 point.ParentPoint = tempStart;
66 point.G = G;
67 point.CalcF();
68 }
69 }
70
71 private void NotFoundPoint(Point tempPoint, Point end, Point point)
72 {
73 point.ParentPoint = tempPoint;
74 point.G = CalcG(tempPoint, point);
75 point.H = CalcH(end, point);
76 point.CalcF();
77 OpenList.Add(point);// This is quite important
78 }
79
80 private int CalcG(Point start, Point point)// Calc the cost from start to point
81 {
82 int G = (Math.Abs(point.X - start.X) + Math.Abs(point.Y - start.Y)) == 1 ? STEP : OBLIQUE;// Should be 1
83 int parentG = point.ParentPoint != null ? point.ParentPoint.G : 0;
84 return G + parentG;
85 }
86
87 private int CalcH(Point end, Point point)// Estimate the cost to reach the target
88 {
89 int step = Math.Abs(point.X - end.X) + Math.Abs(point.Y - end.Y);
90 return step * STEP;
91 }
92
93 public List<Point> GetSurroundPoints(Point point, bool IsIgnoreCorner)
94 {
95 var surroundPoints = new List<Point>(9);
96
97 for (int x = point.X - 1; x <= point.X + 1; x++)
98 {
99 for (int y = point.Y - 1; y <= point.Y + 1; y++)
100 {
101 if (CanReach(point, x, y, IsIgnoreCorner))
102 surroundPoints.Add(x, y);
103 }
104 }
105
106 return surroundPoints;
107 }
108
109 private bool CanReach(int x, int y)
110 {
111 return AStarArray[x, y] == 0;
112 }
113
114 public bool CanReach(Point start, int x, int y, bool IsIgnoreCorner)
115 {
116 if (!CanReach(x, y) || CloseList.Exists(x, y))// Cannot reach or has been handled
117 {
118 return false;
119 }
120 else
121 {
122 if (Math.Abs(x - start.X) + Math.Abs(y - start.Y) == 1)// Adjacent but not diagonal
123 {
124 return true;
125 }
126 else
127 {
128 if (CanReach(Math.Abs(x - 1), y) && CanReach(x, Math.Abs(y - 1)))// Make sure diagnonal but not necessary
129 {
130 return IsIgnoreCorner;
131 }
132 else
133 {
134 return false;
135 }
136 }
137 }
138 }
139 }
140
141 public class Point
142 {
143 public Point ParentPoint { get; set; }
144 public int F { get; set; } // F = G + H
145 public int G { get; set; }
146 public int H { get; set; }
147 public int X { get; set; }
148 public int Y { get; set; }
149
150 public Point(int x, int y)
151 {
152 this.X = x;
153 this.Y = y;
154 }
155
156 public void CalcF()
157 {
158 this.F = this.G + this.H;
159 }
160 }
161
162 public static class ListHelper
163 {
164 public static bool Exists(this List<Point> points, Point point)
165 {
166 foreach (var p in points)
167 if ((p.X == point.X) && (p.Y == point.Y))
168 return true;
169
170 return false;
171 }
172
173 public static bool Exists(this List<Point> points, int x, int y)
174 {
175 foreach (var p in points)
176 if ((p.X == x) && (p.Y == y))
177 return true;
178
179 return false;
180 }
181
182 public static Point MinPoint(this List<Point> points)
183 {
184 points = points.OrderBy(p => p.F).ToList();
185 return points[0];
186 }
187
188 public static void Add(this List<Point> points, int x, int y)
189 {
190 points.Add(new Point(x, y));
191 }
192
193 public static Point Get(this List<Point> points, Point point)
194 {
195 foreach (Point p in points)
196 if ((p.X == point.X) && (p.Y == point.Y))
197 return p;
198
199 return null;
200 }
201
202 public static void Remove(this List<Point> points, int x, int y)
203 {
204 foreach (var point in points)
205 if ((point.X == x) && (point.Y == y))
206 points.Remove(point);
207 }
208 }
209 }
测试代码如下：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace AStarOne
8 {
9 class Program
10 {
11 static void Main(string[] args)
12 {
13 int[,] array = {
14 { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
15 { 1, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 1},
16 { 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1},
17 { 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 1},
18 { 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 1},
19 { 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1},
20 { 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1},
21 { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
22 };
23
24 AStar astar = new AStar(array);
25
26 Point start = new Point(1, 1);
27 Point end = new Point(6, 10);
28 var parent = astar.FindPath(start, end, false);
29
30 Console.WriteLine("Print path:");
31 while (parent != null)
32 {
33 //Console.WriteLine(parent.X + ", " + parent.Y);
34 array[parent.X, parent.Y] = 8;
35 parent = parent.ParentPoint;
36 }
37
38 for (int i = 0; i < 8; i++)
39 {
40 for (int j = 0; j < 12; j++)
41 {
42 Console.Write(array[i,j] + " ");
43 }
44 Console.WriteLine();
45 }
46 }
47 }
48 }
运行结果如下（注意‘8’的位置即是路径）：
时间： 2024-08-26 08:47:54