深度优先+奇偶剪枝 杭电1010

#include<stdio.h>
#include<math.h>
char maze[8][8];
int time, m, n, wall, sx, sy, dx, dy, escape;
int dir[4][2] = {{0,-1},{0,1},{1,0},{-1,0}};

void dfs(sx, sy, t){
    int i, temp;
    if(sx > m || sy > n || sx <= 0 || sy <= 0) return ;
    if(sx == dx && sy == dy && t == time) escape = 1;
    if(escape) return ;
    temp = time - t - abs(sx - dx) - abs(sy - dy);
    if(temp < 0 || temp & 1) return;
    //printf("%d\n", escape);
    for(i = 0; i < 4; i++){
        if(maze[sx+dir[i][0]][sy+dir[i][1]] != 'X'){
            maze[sx+dir[i][0]][sy+dir[i][1]] = 'X';
            dfs(sx+dir[i][0], sy+dir[i][1], t + 1);
            maze[sx+dir[i][0]][sy+dir[i][1]] = '.';
        }
    }

    
}

int main(){
    int i, j;
    while(1){
        wall = 0;
        scanf("%d%d%d", &m, &n , &time);
        if(0 == m && 0 == m && 0 == time) break;
        getchar();
        for(i = 1; i <= m; i++){
            
            for(j = 1; j <= n; j++){
                scanf("%c", &maze[i][j]);
                if('S' == maze[i][j]){
                    sx = i;
                    sy = j;
                }else if('D' == maze[i][j]){
                    dx = i;
                    dy = j;
                }else if('X' == maze[i][j]){
                    wall ++;
                }
                
            }//for(j)
            getchar();
        }//for(i)


        escape = 0;
        maze[sx][sy] = 'X';
        dfs(sx, sy, 0);
        if(escape == 1) printf("YES\n");
        else printf("NO\n");
    }

    
    return 0;
}