mirror of
https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
59 lines
1.4 KiB
C++
59 lines
1.4 KiB
C++
#include<iostream>
|
|
#include<cstdio>
|
|
#include<queue>
|
|
#include<vector>
|
|
#include<cstring>
|
|
#include<map>
|
|
#define MAX_V 110
|
|
#define INF 0x7ffffff
|
|
using namespace std;
|
|
map <string,int> name;
|
|
int ans[MAX_V][MAX_V],d[MAX_V][MAX_V],dd[MAX_V][MAX_V];
|
|
bool ok[MAX_V][MAX_V];
|
|
int main()
|
|
{
|
|
int n,m,a,b;
|
|
while(~scanf("%d%d",&n,&m))
|
|
{
|
|
memset(d,0,sizeof(d));
|
|
memset(ans,0,sizeof(ans));
|
|
memset(ok,0,sizeof(ok));
|
|
while(m--)
|
|
{
|
|
scanf("%d%d",&a,&b);
|
|
ans[a][b]=ans[b][a]=d[a][b]=d[b][a]=1;
|
|
ok[a][b]=ok[b][a]=1;
|
|
}
|
|
int times=6;
|
|
while(times--){
|
|
memset(dd,0,sizeof(dd));
|
|
for(int i=0;i<n;i++){
|
|
for(int j=0;j<n;j++){
|
|
for(int k=0;k<n;k++){
|
|
dd[i][j]+=ans[i][k]*d[k][j];
|
|
}
|
|
}
|
|
}
|
|
for(int i=0;i<n;i++){
|
|
for(int j=0;j<n;j++){
|
|
ans[i][j]=dd[i][j];
|
|
}
|
|
}
|
|
for(int i=0;i<n;i++){
|
|
for(int j=0;j<n;j++){
|
|
if(ans[i][j]!=0) ok[i][j]=1;
|
|
}
|
|
}
|
|
}
|
|
int flag=1;
|
|
for(int i=0;i<n;i++){
|
|
for(int j=0;j<n;j++){
|
|
if(ok[i][j]==0)
|
|
flag=0;
|
|
}
|
|
}
|
|
puts(flag?"Yes":"No");
|
|
}
|
|
return 0;
|
|
}
|