56 lines
994 B
C++
56 lines
994 B
C++
#include<iostream>
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#include<cstdio>
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#include<cstring>
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using namespace std;
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const int N=1005;
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int pre[N],count[N];
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void build(int n)
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{
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int i;
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for(i=1;i<=n;i++) {pre[i]=i;count[i]=0;}
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}
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int find(int k)
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{
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if(pre[k]==k) return k;
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pre[k]=find(pre[k]);
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return pre[k];
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}
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void get_map(int m)
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{
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int a,b,f1,f2;
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while(m--)
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{
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scanf("%d%d",&a,&b);
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f1=find(a);
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f2=find(b);
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if(f1==f2) count[f1]++;
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else
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{
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pre[f2]=f1;
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count[f1]+=count[f2]+1;
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}
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}
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}
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int Judge(int n)
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{
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int flag=0;
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for(int i=1;i<=n;i++)
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{
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if(pre[i]!=i) continue;
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if(count[i]%2) {flag=1;break;}
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}
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return flag;
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}
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int main()
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{
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int n,m;
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while(scanf("%d%d",&n,&m),n||m)
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{
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build(n);
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get_map(m);
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if(Judge(n)) cout<<"No"<<endl;
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else cout<<"Yes"<<endl;
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}
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return 0;
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}
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