题目链接http://acm.hdu.edu.cn/showproblem.php?pid=1181
此题多种方法。比如说Flyod传递闭包 就能搞定 这里只写DFS和BFS
熟悉下。只有DFS是我写的，其他的都是同学的。
DFS
View Code
1 #include <stdio.h> 2 #include <string.h> 3 #include <stdlib.h> 4 #define N 30 5 int m[N][N],flag,visit[N]; 6 void dfs(int n) 7 { 8 int i; 9 if(n=='m'-'a') 10 { 11 flag=1;return; 12 } 13 for(i=0;i<26;i++) 14 { 15 if(m[n][i]==1&&!visit[i]) 16 { 17 visit[i]=1; 18 dfs(i); 19 } 20 } 21 } 22 int main() 23 { 24 char s[100];int len; 25 memset(m,0,sizeof(m)); 26 memset(visit,0,sizeof(visit)); 27 while(scanf("%s",s)&&s[0]!='0') 28 { 29 len=strlen(s); 30 m[s[0]-'a'][s[len-1]-'a']=1; 31 while(scanf("%s",s)&&s[0]!='0') 32 { 33 flag=0; 34 len=strlen(s); 35 m[s[0]-'a'][s[len-1]-'a']=1; 36 } 37 dfs(1); 38 flag== 1 ? printf( "Yes.\n" ) : printf( "No.\n" ); 39 } 40 return 0; 41 }
BFS
View Code
1 #include<stdio.h> 2 #include<string.h> 3 int q[100000]; 4 int map[30][30]; 5 int pro[100000]; 6 int f,r; 7 8 int main() 9 { 10 int n,i,j,len,leap; 11 char s[200]; 12 while(scanf("%s",s) != EOF) 13 { 14 leap = 0; 15 memset(map,0,sizeof(map)); 16 memset(pro,0,sizeof(pro)); 17 memset(q,0,sizeof(q)); 18 len = strlen(s); 19 map[s[0]-'a'][s[len-1]-'a'] = 1; 20 21 while(scanf("%s",s) != EOF) 22 { 23 len = strlen(s); 24 if(s[0] == '0') 25 break; 26 map[s[0]-'a'][s[len-1]-'a'] = 1; 27 } 28 f = 0,r = 0; 29 q[r++] = 'b'-'a'; 30 while(f < r) 31 { 32 int v; 33 v = q[f++]; 34 for(i = 0;i < 26;i++) 35 { 36 if(map[v][i] && !pro[i]) 37 { 38 if(i == 'm'-'a') 39 { 40 leap = 1; 41 break; 42 } 43 q[r++] = i; 44 pro[i] = 1; 45 } 46 } 47 if(leap) 48 break; 49 } 50 if(leap) 51 puts("Yes."); 52 else 53 puts("No."); 54 } 55 return 0; 56 }
用STL queue实现队列的 BFS
View Code
1 #include <queue> 2 #include <cstdio> 3 #include <cstring> 4 #include <iostream> 5 using namespace std; 6 7 const int N=1001; 8 int map[N][N]; 9 int vis[N]; 10 queue<int>q; 11 12 int bfs() 13 { 14 while(!q.empty()) 15 { 16 int a; 17 a=q.front(); 18 q.pop(); 19 for(int i=0;i<26;i++) 20 { 21 if(map[a][i]&&!vis[i]) 22 { 23 if(i=='m'-'a') 24 { 25 return 1; 26 } 27 q.push(i); 28 vis[i]=1; 29 } 30 } 31 } 32 return 0; 33 } 34 35 int main() 36 { 37 int len; 38 char s[N]; 39 while(~scanf("%s",s)) 40 { 41 while(!q.empty()) 42 q.pop(); 43 memset(map,0,sizeof(map)); 44 memset(vis,0,sizeof(vis)); 45 len=strlen(s); 46 map[s[0]-'a'][s[len-1]-'a']=1; 47 while(~scanf("%s",s)) 48 { 49 len=strlen(s); 50 if(s[0]=='0') 51 break; 52 map[s[0]-'a'][s[len-1]-'a']=1; 53 } 54 q.push('b'-'a'); 55 if(bfs()) 56 puts("Yes."); 57 else 58 puts("No."); 59 } 60 return 0; 61 }