RQNOJ 195校园迷宫(简单BFS)

 1 /*  

 2 *  简单BFS  

 3 */

 4 

 5 #include <cstdio>

 6 #include <cstring>

 7 #include <iostream>

 8 

 9 using namespace std;

10 

11 const int N = 2005;

12 

13 int map[N][N];

14 bool vis[N][N];

15 struct node {

16     int x;

17     int y;

18     int c;

19 }Q[N*N], s, e;

20 int front, rear;

21 int dir[4][2] = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};

22 

23 int BFS(int n, int m) {

24     node first, next;

25     memset(vis, true, sizeof(vis));

26     front = rear = 0;

27     vis[s.x][s.y] = false;

28     Q[front++] = s;

29     while (rear < front) {

30         first = Q[rear++];

31         if (first.x==e.x && first.y==e.y) return first.c;

32         for (int i=0; i<4; ++i) {

33             next.x = first.x + dir[i][0];

34             next.y = first.y + dir[i][1];

35             next.c = first.c + 1;

36             if (next.x>=0&&next.x<n&&next.y>=0&&next.y<m&&vis[next.x][next.y]&&map[next.x][next.y]==0) {

37                 Q[front++] = next;

38                 vis[next.x][next.y] = false;

39             }

40         }

41     }

42     return -1;

43 }

44 

45 int main() {

46     int n, m;

47     while (scanf("%d%d", &n, &m) != EOF) {

48         for (int i=0; i<n; ++i) {

49             for (int j=0; j<m; ++j) scanf ("%d", &map[i][j]);

50         }        

51         scanf ("%d%d%d%d", &s.x, &s.y, &e.x, &e.y);

52         --s.x, --s.y, --e.x, --e.y;

53         s.c = 0;

54         int ans = BFS(n, m);

55         if (ans < 0) printf ("No Answer!\n");

56         else printf ("%d\n", ans);

57     }

58     return 0;

59 }