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