【HDOJ】2822 Dogs

bfs.

 1 /* 2822 */
 2 #include <iostream>
 3 #include <cstdio>
 4 #include <cstring>
 5 #include <cstdlib>
 6 #include <queue>
 7 using namespace std;
 8
 9 #define MAXN 1005
10 #define INF 0xffffff
11
12 typedef struct node_t {
13     int d, x, y;
14     node_t() {}
15     node_t(int xx, int yy, int dd) {
16         x = xx; y = yy; d = dd;
17     }
18     friend bool operator <(node_t a, node_t b) {
19         return a.d > b.d;
20     }
21 } node_t;
22
23 int visit[MAXN][MAXN];
24 char map[MAXN][MAXN];
25 int n, m;
26 int bx, by, ex, ey;
27 int dir[4][2] = {
28     -1,0,1,0,0,1,0,-1
29 };
30
31 inline bool check(int x, int y) {
32     return x<0 || x>=n || y<0 || y>=m;
33 }
34
35 int bfs() {
36     int x = bx, y = by, d = 0;
37     int i, j, k;
38     priority_queue<node_t> Q;
39     node_t nd;
40
41     Q.push(node_t(x, y, d));
42     visit[x][y] = 0;
43
44     while (!Q.empty()) {
45         nd = Q.top();
46         if (nd.x==ex && nd.y==ey)
47             return nd.d;
48         Q.pop();
49         for (i=0; i<4; ++i) {
50             x = nd.x + dir[i][0];
51             y = nd.y + dir[i][1];
52             if (check(x, y))
53                 continue;
54             if (map[x][y] == ‘X‘)
55                 d = nd.d;
56             else
57                 d = nd.d + 1;
58             if (d < visit[x][y]) {
59                 visit[x][y] = d;
60                 Q.push(node_t(x, y, d));
61             }
62         }
63     }
64
65     return 0;
66 }
67
68 int main() {
69     int i, j, k;
70
71     #ifndef ONLINE_JUDGE
72         freopen("data.in", "r", stdin);
73     #endif
74
75     while (scanf("%d %d", &n, &m)!=EOF && (n||m)) {
76         for (i=0; i<n; ++i) {
77             scanf("%s", map[i]);
78             for (j=0; j<m; ++j)
79                 visit[i][j] = INF;
80         }
81         scanf("%d%d%d%d",&bx,&by,&ex,&ey);
82         --bx; --by; --ex; --ey;
83         k = bfs();
84         printf("%d\n", k);
85     }
86
87     return 0;
88 }