OJ-Problems-Source/HDOJ/5424_autoAC.cpp

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#include <iostream>
#include<cstring>
#include<cstdio>
using namespace std;
int n,cnt,x,y,deg[1001];
bool flag,vis[1001],Map[1001][1001];
void dfs(int u)
{
if(cnt==n) {flag=1;return;}
for(int i=1;i<=n&&!flag;++i)
if(!vis[i]&&Map[u][i])
{
vis[i]=1;
++cnt;
dfs(i);
--cnt;
vis[i]=0;
}
}
int main()
{
while(~scanf("%d",&n))
{
flag=0;
cnt=1;
memset(deg,0,sizeof(deg));
memset(vis,0,sizeof(vis));
memset(Map,0,sizeof(Map));
for(int i=0;i<n;++i){
scanf("%d%d",&x,&y);
if(x!=y&&!Map[x][y])
{
Map[x][y]=Map[y][x]=1;
++deg[x],++deg[y];
}
}
int s=1,tot=0;
for(int i=1;i<=n;++i)
if(deg[i]==1) {s=i;++tot;}
if(tot>2) {puts("NO");continue;}
vis[s]=1;
dfs(s);
if(flag) puts("YES");
else puts("NO");
}
return 0;
}