【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[4][2] = {
    -1,0,1,0,0,1,0,-1
};

inline bool check(int x, int y) {
    return x<0 || x>=n || y<0 || y>=m;
}

int bfs() {
    int x = bx, y = by, d = 0;
    int i, j, k;
    priority_queue<node_t> Q;
    node_t nd;
    
    Q.push(node_t(x, y, d));
    visit[x][y] = 0;
    
    while (!Q.empty()) {
        nd = Q.top();
        if (nd.x==ex && nd.y==ey)
            return nd.d;
        Q.pop();
        for (i=0; i<4; ++i) {
            x = nd.x + dir[i][0];
            y = nd.y + dir[i][1];
            if (check(x, y))
                continue;
            if (map[x][y] == 'X')
                d = nd.d;
            else
                d = nd.d + 1;
            if (d < visit[x][y]) {
                visit[x][y] = d;
                Q.push(node_t(x, y, d));
            }
        }
    }
    
    return 0;
}

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=0; i<n; ++i) {
            scanf("%s", map[i]);
            for (j=0; j<m; ++j)
                visit[i][j] = INF;
        }
        scanf("%d%d%d%d",&bx,&by,&ex,&ey);
        --bx; --by; --ex; --ey;
        k = bfs();
        printf("%d
", k);
    }
    
    return 0;
}