52 lines
1.0 KiB
C++
52 lines
1.0 KiB
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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int n,m,map[20][20];
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int root[20],flag;
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void DFS(int x,int y){
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if(flag)
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return ;
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if(y>m)
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return ;
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if(x==n){
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flag=1;
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return ;
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}
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for(int i=0;i<x;i++){
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if(root[i]!=i)
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continue;
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int tag=1;
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for(int j=i;j<x && tag;j++)
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if(root[j]==i)
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tag=map[j][x];
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if(tag){
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root[x]=i;
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DFS(x+1,y);
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root[x]=x;
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}
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}
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DFS(x+1,y+1);
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}
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int main(){
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while(~scanf("%d%d",&n,&m)){
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memset(map,0,sizeof(map));
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flag=0;
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int k,x;
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for(int i=0;i<n;i++){
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scanf("%d",&k);
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root[i]=i;
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while(k--){
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scanf("%d",&x);
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map[i][x]=1;
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}
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}
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DFS(0,0);
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if(m>=n || flag)
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puts("YES");
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else
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puts("NO");
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}
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return 0;
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}
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