刚开始想写最短路 没写出来 TLE了在最后一组数据上 加了点优化过了 从两个出口出 像各点BFS 取最小中的最大值
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1 /* 2 ID: shangca2 3 LANG: C++ 4 TASK: maze1 5 */ 6 #include <iostream> 7 #include<cstdio> 8 #include<cstring> 9 #include<algorithm> 10 #include<stdlib.h> 11 #include<queue> 12 using namespace std; 13 char str[300][210]; 14 int n,m,f[300][210],dis[4][2] = {0,1,0,-1,1,0,-1,0}; 15 struct node 16 { 17 int x,y,num; 18 }; 19 int bfs(int x,int y,int xx,int yy,int o) 20 { 21 int i; 22 queue<node>q; 23 memset(f,0,sizeof(f)); 24 node t1; 25 t1.x = x; 26 t1.y = y; 27 t1.num = 0; 28 f[x][y] = 1; 29 q.push(t1); 30 while(!q.empty()) 31 { 32 node t2 = q.front(); 33 if(t2.num>o) 34 return o; 35 q.pop(); 36 if(t2.x==xx&&t2.y == yy) 37 { 38 int kk = t2.num; 39 return kk; 40 } 41 for(i = 0 ; i < 4 ; i++) 42 { 43 int tx = t2.x+dis[i][0]; 44 int ty = t2.y+dis[i][1]; 45 if(str[tx][ty]==' '&&!f[tx][ty]&&(tx>0&&tx<2*m&&ty>0&&ty<2*n)) 46 { 47 f[tx][ty] = 1; 48 tx = tx+dis[i][0]; 49 ty = ty+dis[i][1]; 50 f[tx][ty] = 1; 51 t1.num = t2.num+1; 52 t1.x = tx; 53 t1.y = ty; 54 q.push(t1); 55 } 56 } 57 } 58 } 59 int main() 60 { 61 freopen("maze1.in","r",stdin); 62 freopen("maze1.out","w",stdout); 63 int i,j,k,g=0,e[10]; 64 scanf("%d%d",&n,&m); 65 for(i = 0; i < 2*m+1 ; i++) 66 { 67 getchar(); 68 for(j = 0 ; j < 2*n+1 ; j++) 69 { 70 scanf("%c",&str[i][j]); 71 if(i==0&&str[i][j]==' ') 72 { 73 e[++g] = i+1; 74 e[++g] = j; 75 } 76 if(i==2*m&&str[i][j]==' ') 77 { 78 e[++g] = i-1; 79 e[++g] = j; 80 } 81 if(j==0&&str[i][j]==' ') 82 { 83 e[++g] = i; 84 e[++g] = j+1; 85 } 86 if(j==2*n&&str[i][j]==' ') 87 { 88 e[++g] = i; 89 e[++g] = j-1; 90 } 91 } 92 } 93 int m1=0,m2=0; 94 for(i = 0 ; i < 2*m+1 ; i++) 95 for(j = 0 ; j < 2*n+1 ;j++) 96 { 97 if(i%2==1&&j%2==1) 98 { 99 int k1 = bfs(e[1],e[2],i,j,100000000); 100 if(k1<m2) 101 continue ; 102 int k2 = bfs(e[3],e[4],i,j,k1); 103 m1 = min(k2,k1); 104 m2 = max(m1,m2); 105 } 106 } 107 printf("%d\n",m2+1); 108 return 0; 109 }