75 lines
1.4 KiB
C++
75 lines
1.4 KiB
C++
#include<iostream>
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#include<cstring>
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#include<algorithm>
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#include<cstdlib>
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#include<vector>
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#include<cmath>
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#include<stdlib.h>
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#include<iomanip>
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#include<list>
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#include<deque>
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#include<map>
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#include <stdio.h>
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#include <queue>
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#include <stack>
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#define maxn 100010
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#define ull unsigned long long
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#define ll long long
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#define reP(i,n) for(i=1;i<=n;i++)
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#define rep(i,n) for(i=0;i<n;i++)
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#define cle(a) memset(a,0,sizeof(a))
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#define mod 90001
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#define PI 3.141592657
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#define INF 1<<30
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const ull inf = 1LL << 61;
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const double eps=1e-5;
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using namespace std;
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bool cmp(int a,int b)
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{
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return a>b;
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}
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int fa[maxn];
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int ans,cnt;
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int mark[maxn];
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void init(){
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for(int i=0;i<=maxn;i++)
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fa[i]=-1;
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ans=0;cnt=0;
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cle(mark);
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}
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int findfa(int x){
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while(fa[x]>=0)
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x=fa[x];
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return x;
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}
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void Union(int x,int y){
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int fa_x=findfa(x);
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int fa_y=findfa(y);
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if(fa_x!=fa_y)
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fa[fa_x]=fa_y;
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else{
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ans++;
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}
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mark[x]=mark[y]=1;
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}
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int x,y;
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int main()
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{
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init();
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while(cin>>x>>y){
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if(x==-1&&y==-1)break;
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if(x==0&&y==0){
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for(int i=1;i<=maxn;i++){
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if((mark[i])&&(fa[i]==-1))
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cnt++;
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}
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if(ans>0||cnt>1)printf("No\n");
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else printf("Yes\n");
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init();
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continue;
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}
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Union(x,y);
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}
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return 0;
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}
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