#include<cstdio>
#include<cmath>
#include<cstring>
int a[1005][1005];
using namespace std;
int main()
{
int n,flag=0;
cin>>n;
for(int i=0;i<n;i++)
for(int j=0;j<n;j++)
cin>>a[i][j];
for(int i=0;i<n;i++)
{
for(int j=0;j<n;j++)
{
if(a[i][j]==0&&i>j)
flag=0;
else
flag=1;
}
}
if(flag==1)
{
cout<<"YES"<<endl;
}
else
{
cout<<"NO"<<endl;
}
return 0;
}
哪位大神帮忙看看错在哪里了·-·
一直是60分········································
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