【HDOJ】2822 Dogs

bfs.

 /* 2822 */
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 #include <queue>
 using namespace std;

 #define MAXN 1005
 #define INF 0xffffff

 typedef struct node_t {
     int d, x, y;
     node_t() {}
     node_t(int xx, int yy, int dd) {
         x = xx; y = yy; d = dd;
     }
     friend bool operator <(node_t a, node_t b) {
         return a.d > b.d;
     }
 } node_t;

 int visit[MAXN][MAXN];
 char map[MAXN][MAXN];
 int n, m;
 int bx, by, ex, ey;
 int dir[][] = {
     -,,,,,,,-
 };

 inline bool check(int x, int y) {
     return x< || x>=n || y< || y>=m;
 }

 int bfs() {
     int x = bx, y = by, d = ;
     int i, j, k;
     priority_queue<node_t> Q;
     node_t nd;

     Q.push(node_t(x, y, d));
     visit[x][y] = ;

     while (!Q.empty()) {
         nd = Q.top();
         if (nd.x==ex && nd.y==ey)
             return nd.d;
         Q.pop();
         for (i=; i<; ++i) {
             x = nd.x + dir[i][];
             y = nd.y + dir[i][];
             if (check(x, y))
                 continue;
             if (map[x][y] == 'X')
                 d = nd.d;
             else
                 d = nd.d + ;
             if (d < visit[x][y]) {
                 visit[x][y] = d;
                 Q.push(node_t(x, y, d));
             }
         }
     }

     return ;
 }

 int main() {
     int i, j, k;

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
     #endif

     while (scanf("%d %d", &n, &m)!=EOF && (n||m)) {
         for (i=; i<n; ++i) {
             scanf("%s", map[i]);
             for (j=; j<m; ++j)
                 visit[i][j] = INF;
         }
         scanf("%d%d%d%d",&bx,&by,&ex,&ey);
         --bx; --by; --ex; --ey;
         k = bfs();
         printf("%d\n", k);
     }

     return ;
 }