BFS。wa了一下午，原来是YES，写成了Yes。
1 #include <iostream>
2 #include <cstdio>
3 #include <cstring>
4 #include <queue>
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<node_st> 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 else
86 printf("NO\n");
87 }
88 }
89
90 return 0;
91 }
时间： 2024-08-07 08:47:07