Poj 3626 BFS

 

 1 #include <math.h>
 2 #include <stdio.h>
 3 #include <stdlib.h>
 4 #include <string.h>
 5 #include <memory.h>
 6 
 7 int mat[1010][1010];
 8 int i, nNum, tx, ty, ai, bi;
 9 int dx[] = {-1, 1, 0, 0};
10 int dy[] = {0, 0, -1, 1};
11 
12 struct path
13 {
14     int x, y, step;
15 }q[1000010]={0};
16 
17 int IsInBound(int x, int y)
18 {
19     if (x<0 || y<0|| x>1000 || y>1000)
20     {
21         return 0;
22     }
23     
24     return 1;
25 }/* IsInBound */
26 
27 void BFS()
28 {
29     int rear = -1;
30     int k, front = -1;
31     struct path cur, next;
32     
33     cur.x = 500;
34     cur.y = 500;
35     cur.step = 0;
36     q[++rear] = cur;
37     
38     mat[500][500] = 1;
39     while (front < rear)
40     {
41         cur = q[++front];
42         if (cur.x==500-ty && cur.y==500+tx)
43         {
44             printf("%d\n", cur.step);
45             break;
46         }/* End of If */
47         
48         for (k=0; k<4; ++k)
49         {
50             next.x = cur.x + dx[k];
51             next.y = cur.y + dy[k];
52             if (IsInBound(next.x, next.y) && mat[next.x][next.y]==0)
53             {
54                 mat[next.x][next.y] = 1;
55                 next.step = cur.step + 1;
56                 q[++rear]  = next;
57             }
58         }/* End of For */
59     }/* End of WHile */
60 }/* BFS */
61 
62 int main()
63 {
64     while (3 == scanf("%d %d %d", &tx, &ty, &nNum))
65     {
66         memset(mat, 0, sizeof(mat));
67         for (i=0; i<nNum; ++i)
68         {
69             scanf("%d %d", &ai, &bi);
70             mat[500-bi][500+ai] = 1;
71         }/* End of For */
72         
73         BFS();
74     }/* End of While */
75     
76     return 0;
77 }