bfs.题目做的不细心，好多小错误。尤其注意起始点就是边界的情况。wa了八次。
1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 #include <queue> 5 using namespace std; 6 7 #define MAXN 85 8 9 typedef struct node_st { 10 int x, y; 11 int d, s; 12 node_st() {} 13 node_st(int xx, int yy, int dd, int ss) { 14 x = xx; y = yy; d = dd; s = ss; 15 } 16 } node_st; 17 18 char map[MAXN][MAXN]; 19 bool visit[4][MAXN][MAXN]; 20 int direct[4][2] = {-1,0,1,0,0,-1,0,1}; 21 int n, m; 22 23 int bfs(int sx, int sy) { 24 int i, j, nx, ny; 25 queue<node_st> que; 26 node_st node; 27 bool flag; 28 29 if (sx==0 || sx==n-1 || sy==0 || sy==m-1) 30 return 0; 31 memset(visit, false, sizeof(visit)); 32 visit[0][sx][sy] = visit[1][sx][sy] = visit[2][sx][sy] = visit[3][sx][sy] = true; 33 34 for (i=0; i<4; ++i) { 35 nx = sx + direct[i][0]; 36 ny = sy + direct[i][1]; 37 if (nx<0 || nx>=n || ny<0 || ny>=m) 38 continue; 39 if (map[nx][ny] != '#') { 40 que.push(node_st(nx, ny, i, 1)); 41 visit[i][nx][ny] = true; 42 } 43 } 44 45 while ( !que.empty() ) { 46 node = que.front(); 47 que.pop(); 48 flag = true; 49 // node.d = 0/1 -> south/north 50 // node.d = 2/3 -> east/west 51 j = (node.d&2) ? 0:2; 52 for (i=j; i<j+2; ++i) { 53 nx = node.x + direct[i][0]; 54 ny = node.y + direct[i][1]; 55 if (nx<0 || nx>=n || ny<0 || ny>=m) 56 continue; 57 if (map[nx][ny] != '#') { 58 flag = false; 59 if (!visit[i][nx][ny]) { 60 if (nx==0 || nx==n-1 || ny==0 || ny==m-1) 61 return node.s+1; 62 que.push(node_st(nx, ny, i, node.s+1)); 63 visit[i][nx][ny] = true; 64 } 65 } 66 } 67 if (flag) { 68 i = node.d; 69 nx = node.x + direct[i][0]; 70 ny = node.y + direct[i][1]; 71 if (nx<0 || nx>=n || ny<0 || ny>=m) 72 continue; 73 if (map[nx][ny]=='#' || visit[i][nx][ny]) 74 continue; 75 if(nx==0 || nx==n-1 || ny==0 || ny==m-1) 76 return node.s+1; 77 que.push(node_st(nx, ny, i, node.s+1)); 78 visit[i][nx][ny] = true; 79 } 80 } 81 return -1; 82 } 83 84 int main() { 85 int t, x, y; 86 int i, j; 87 88 scanf("%d", &t); 89 90 while (t--) { 91 scanf("%d %d", &n, &m); 92 for (i=0; i<n; ++i) { 93 scanf("%s", map[i]); 94 for (j=0; j<m; ++j) 95 if (map[i][j] == '@') { 96 x = i; 97 y = j; 98 } 99 } 100 printf("%d ", bfs(x, y)); 101 } 102 103 return 0; 104 }