hdu1181 dfs 字符串首尾可拼接，问是否可寻找到一条字串路径使得首尾分别是‘b’和‘m’,简单的搜索+回溯

 #include<bits/stdc++.h>
 using namespace std;
 typedef unsigned int ui;
 typedef long long ll;
 typedef unsigned long long ull;
 #define pf printf
 #define prime1 1e9+7
 #define prime2 1e9+9
 #define scand(x) scanf("%llf",&x)
 #define f(i,a,b) for(int i=a;i<=b;i++)
 #define scan(a) scanf("%d",&a)
 #define dbg(args) cout<<#args<<":"<<args<<endl;
 #define pb(i) push_back(i)
 #define ppb(x) pop_back(x)
 #define maxn 100005
 int m,t,tot;
 struct node{
     char st,ed;
 }n[maxn];
 char s[maxn];
 bool vis[maxn];
 bool dfs(char a)
 {
     if(a=='m')return true;
     f(i,,tot-)
     {
         if(n[i].st==a&&!vis[i])
         {
             vis[i]=true;
             if(dfs(n[i].ed))return true;
             vis[i]=false;
         }
     }
     return false;
 }
 int main()
 {
     std::ios::sync_with_stdio(false);
     while(scanf("%s",s)==)
     {
         if(strcmp(s,"")==)
         {
             if(dfs('b'))
             {
                 pf("Yes.\n");
             }
             else pf("No.\n");
             tot=;
             memset(vis,false,sizeof(vis));
             continue;
         }
         n[tot].st=s[];
         n[tot].ed=s[strlen(s)-];
         tot++;
     }
  }