A*算法实现（图形化表示）——C++描述

概要

　　A*算法是一种启发式寻路算法，BFS是一种盲目的无目标的搜索算法，相比于BFS，A*算法根据适应度构建优先队列，根据适应度值可以很好的向目标点移动，具体详情，请看搜索相关文档，我在只是实现了在无障碍的情况下的A*算法，有障碍的情况类似。

开发环境

　　visual studio 2017 + eaysX

实现

  1 #include<stdio.h>
  2 #include<vector>
  3 #include<queue>
  4 #include<graphics.h>
  5 #include<stdlib.h>
  6 #include<time.h>
  7 #include<unordered_set>
  8 
  9 using namespace std;
 10 
 11 const int WIDTH_BLOCK_NUM = 20;
 12 const int HEIGHT_BLOCK_NUM = 20;
 13 const int WINDOWS_WIDTH = 800;
 14 const int WINDOWS_HEIGHT = 800;
 15 const int MAX_MARK = 20;
 16 const int MIN_MARK = 0;
 17 
 18 int dir_x[] = { 1,1,1,0,0,-1,-1,-1 };
 19 int dir_y[] = { 1,-1,0,1,-1,1,-1,0 };
 20 
 21 struct Block
 22 {
 23 public:
 24     int x, y;
 25     int f;
 26     int g;
 27     Block(int x, int y, int f, int g)
 28     {
 29         this->x = x;
 30         this->y = y;
 31         this->f = f;
 32         this->g = g;
 33     }
 34     Block() {}
 35     friend bool operator<(Block a, Block b) {
 36         return a.f + a.g > b.f + b.g;
 37     }
 38 };
 39 priority_queue<Block>pq;
 40 vector<Block>vec;
 41 vector<Block>local_vec;
 42 unordered_set<int>us;
 43 Block start_block, end_block;
 44 
 45 
 46 
 47 int randInt(int left, int right);
 48 void init();
 49 void draw();
 50 void position2rectangle(struct Block&b, int rect[][2]);
 51 bool is_valid(int x, int y);
 52 int position2mark(int x, int y);
 53 
 54 
 55 int main()
 56 {
 57     srand(time(NULL));
 58     init();
 59     initgraph(WINDOWS_WIDTH, WINDOWS_HEIGHT);
 60     Block temp = start_block;
 61     pq.push(temp);
 62     us.insert(position2mark(temp.x, temp.y));
 63 
 64     while (!(temp.x == end_block.x&&temp.y == end_block.y))
 65     {
 66         temp = pq.top();
 67         pq.pop();
 68         vec.push_back(temp);
 69         for (int i = 0; i < 8; ++i) {
 70             int temp_x = temp.x + dir_x[i];
 71             int temp_y = temp.y + dir_y[i];
 72             if (is_valid(temp_x, temp_y) && !us.count(position2mark(temp_x, temp_y))) {
 73                 Block b;
 74                 b.x = temp_x;
 75                 b.y = temp_y;
 76                 b.f = temp.f + (abs(dir_x[i]) + abs(dir_y[i])) > 1 ? 14 : 10;
 77                 b.g = (abs(temp_x - end_block.x) + abs(temp_y - end_block.y)) * 10;
 78                 pq.push(b);
 79                 us.insert(position2mark(temp_x, temp_y));
 80                 local_vec.push_back(b);
 81             }
 82         }
 83         draw();
 84     }
 85     closegraph();
 86     return 0;
 87 }
 88 
 89 int randInt(int left, int right)
 90 {
 91     return rand() % (right - left + 1) + left;
 92 }
 93 
 94 void init()
 95 {
 96     start_block.x = randInt(MIN_MARK, MAX_MARK);
 97     start_block.y = randInt(MIN_MARK, MAX_MARK);
 98     end_block.x = randInt(MIN_MARK, MAX_MARK);
 99     end_block.y = randInt(MIN_MARK, MAX_MARK);
100     while (start_block.x==end_block.x||start_block.y==end_block.y)
101     {
102         end_block.x = randInt(MIN_MARK, MAX_MARK);
103         end_block.y = randInt(MIN_MARK, MAX_MARK);
104     }
105 }
106 
107 void draw()
108 {
109     int width = WINDOWS_WIDTH / WIDTH_BLOCK_NUM;
110     int height = WINDOWS_HEIGHT / HEIGHT_BLOCK_NUM;
111     for (int i = 0; i < WINDOWS_WIDTH; i += width)
112     {
113         line(i, 0, i, WINDOWS_HEIGHT);
114     }
115 
116     for (int i = 0; i < WINDOWS_HEIGHT; i += height)
117     {
118         line(0, i, WINDOWS_WIDTH, i);
119     }
120     int arr[2][2];
121     COLORREF prev_color = getfillcolor();
122     
123     setfillcolor(BLUE);
124     for (Block b : local_vec)
125     {
126         position2rectangle(b, arr);
127         fillrectangle(arr[0][0], arr[0][1], arr[1][0], arr[1][1]);
128     }
129 
130 
131     setfillcolor(RED);
132     for (Block b : vec)
133     {
134         position2rectangle(b, arr);
135         fillrectangle(arr[0][0], arr[0][1], arr[1][0], arr[1][1]);
136     }
137 
138     
139 
140     setfillcolor(GREEN);
141     position2rectangle(start_block, arr);
142     fillrectangle(arr[0][0], arr[0][1], arr[1][0], arr[1][1]);
143     position2rectangle(end_block, arr);
144     fillrectangle(arr[0][0], arr[0][1], arr[1][0], arr[1][1]);
145 
146     setfillcolor(prev_color);
147     Sleep(1000);
148 }
149 
150 void position2rectangle(struct Block&b, int rect[][2])
151 {
152     int width = WINDOWS_WIDTH / WIDTH_BLOCK_NUM;
153     int height = WINDOWS_HEIGHT / HEIGHT_BLOCK_NUM;
154     int temp_x = b.x*width;
155     int temp_y = b.y*height;
156     rect[0][0] = temp_x;
157     rect[0][1] = temp_y;
158     rect[1][0] = temp_x + width;
159     rect[1][1] = temp_y + height;
160 }
161 
162 bool is_valid(int x, int y)
163 {
164     if (x < 0 || y < 0 || x >= WIDTH_BLOCK_NUM || y >= HEIGHT_BLOCK_NUM) {
165         return false;
166     }
167     return true;
168 }
169 
170 int position2mark(int x, int y)
171 {
172     return x + y * WIDTH_BLOCK_NUM;
173 }

运行展示