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,0,tot-1)
    {
        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)==1)
    {
        if(strcmp(s,"0")==0)
        {
            if(dfs('b'))
            {
                pf("Yes.
");
            }
            else pf("No.
");
            tot=0;
            memset(vis,false,sizeof(vis));
            continue;
        }
        n[tot].st=s[0];
        n[tot].ed=s[strlen(s)-1];
        tot++;
    }
 }