BFS。wa了一下午，原来是YES，写成了Yes。

1 #include 
     
       2 #include 
      
        3 #include 
       
         4 #include 
        
          5 using namespace std; 6  7 typedef struct node_st{ 8     int x, y; 9     int dir;10     int turn;11     node_st() {}12     node_st(int xx, int yy, int ddir, int tturn) {13         x = xx; y = yy; dir = ddir; turn = tturn;14     }15 } node_st;16 17 int map[1005][1005];18 int n, m;19 int dirs[4][2] = {
   {
   0,1},{
   0,-1},{
   1,0},{-1,0}};20 char turns[1005][1005];21 22 bool bfs(int bx, int by, int ex, int ey) {23     queue
         
           que;24     bool val = false;25     node_st node;26     int x, y, dir, turn;27 28     memset(turns, 0, sizeof(turns));29     turns[bx][by] = 1;30     que.push(node_st(bx, by, -1, 0));31 32     while ( !que.empty() ) {33         node = que.front();34         //printf("x=%d, y=%d, dir=%d, turn=%d\n", node.x, node.y, node.dir, node.turn);35         if (node.x == ex && node.y == ey) {36             val = true;37             break;38         }39         que.pop();40         for (int i=0; i<4; ++i) {41             x = node.x + dirs[i][0];42             y = node.y + dirs[i][1];43             dir = i;44             turn = node.turn;45             if (x<1 || x>n || y<1 || y>m)46                 continue;47             if (map[x][y] && (x!=ex || y!=ey))48                 continue;49             if (dir!=node.dir && node.dir!=-1)50                 ++turn;51             //printf("\tx=%d, y=%d, dir=%d, turn=%d\n", x, y, dir, turn);52             if (turn > 2)53                 continue;54             if (turns[x][y]==0 || turn+1 <= turns[x][y]) {55                 turns[x][y] = turn+1;56                 que.push(node_st(x, y, dir, turn));57             }58         }59     }60 61     return val;62 }63 64 int main() {65     int q, x1, x2, y1, y2;66     int i, j;67 68     while (scanf("%d %d", &n, &m)!=EOF && (n||m)) {69         for (i=1; i<=n; ++i)70             for (j=1; j<=m; ++j)71                 scanf("%d", &map[i][j]);72         scanf("%d", &q);73         while (q--) {74             scanf("%d %d %d %d", &x1, &y1, &x2, &y2);75             if (x1==x2 && y1==y2) {76                 printf("NO\n");77                 continue;78             }79             if (map[x1][y1]!=map[x2][y2] || map[x1][y1]==0 || map[x2][y2]==0) {80                 printf("NO\n");81                 continue;82             }83             if ( bfs(x1, y1, x2, y2) )84                 printf("YES\n");85             else86                 printf("NO\n");87         }88     }89 90     return 0;91 }