【HDOJ】2757 Ocean Currents

简单BFS。

  1 /* 2757 */
  2 #include <iostream>
  3 #include <queue>
  4 #include <cstdio>
  5 #include <cstring>
  6 #include <cstdlib>
  7 using namespace std;
  8 
  9 #define MAXN 1005
 10 
 11 typedef struct node_t {
 12     int k, t;
 13     node_t() {}
 14     node_t(int kk, int tt) {
 15         k = kk; t = tt;
 16     }
 17     friend bool operator <(const node_t &a, const node_t &b) {
 18         return a.t > b.t;
 19     }
 20 } node_t;
 21 
 22 int n, m;
 23 int bx, by, ex, ey;
 24 char map[MAXN][MAXN];
 25 int visit[MAXN][MAXN];
 26 int dir[8][2] = {
 27     -1,0, -1,1, 0,1, 1,1,
 28     1,0, 1,-1, 0,-1, -1,-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 xx, yy;
 37     int x, y, t;
 38     int i, j, k;
 39     node_t nd;
 40     priority_queue<node_t> Q;
 41     
 42     memset(visit, 0x3f, sizeof(visit));
 43     visit[bx][by] = 0;
 44     nd.t = 0;
 45     nd.k = bx*1000+by;
 46     Q.push(nd);
 47     
 48     while (!Q.empty()) {
 49         nd = Q.top();
 50         xx = nd.k/1000;
 51         yy = nd.k%1000;
 52         if (xx==ex && yy==ey)
 53             return nd.t;
 54         Q.pop();
 55         for (i=0; i<8; ++i) {
 56             x = xx + dir[i][0];
 57             y = yy + dir[i][1];
 58             if (check(x, y))
 59                 continue;
 60             if (map[xx][yy] == i)
 61                 t = nd.t;
 62             else
 63                 t = nd.t + 1;
 64             if (visit[x][y] > t) {
 65                 visit[x][y] = t;
 66                 k = 1000*x+y;
 67                 Q.push(node_t(k, t));
 68             }
 69         }
 70     }
 71     
 72     return 0;
 73 }
 74 
 75 int main() {
 76     int i, j, k;
 77     int t;
 78     
 79     #ifndef ONLINE_JUDGE
 80         freopen("data.in", "r", stdin);
 81         freopen("data.out", "w", stdout);
 82     #endif
 83     
 84     while (scanf("%d%d",&n,&m) != EOF) {
 85         for(i=0; i<n; ++i) {
 86             scanf("%s", map[i]);
 87             for (j=0; j<m; ++j)
 88                 map[i][j] -= '0';
 89         }
 90         scanf("%d", &t);
 91         while (t--) {
 92             scanf("%d%d%d%d",&bx,&by,&ex,&ey);
 93             --bx; --by; --ex; --ey;
 94             if (bx==ex && by==ey)
 95                 k = 0;
 96             else
 97                 k = bfs();
 98             printf("%d\n", k);
 99         }
100     }
101 
102     return 0;
103 }

 

posted on 2015-02-24 17:21  Bombe  阅读(137)  评论(0)  编辑  收藏  举报

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