#include<bits/stdc++.h>
using namespace std;

int read() {
	char ch=getchar();
	int f=1,x=0;
	while(ch<'0'||ch>'9') {
		if(ch=='-')
			f=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9') {
		x=x*10+ch-'0';
		ch=getchar();
	}
	return f*x;
}
char read_char() {
	char ch=getchar();
	while(!isalpha(ch)) {
		ch=getchar();
	}
	return ch;
}

const int MAXN=500+10;
int n,tot;
int f[MAXN][MAXN],x[MAXN*MAXN],y[MAXN*MAXN],a[MAXN][MAXN];

void solve() {
	cin>>n;
	tot=0;
	for(int i=1;i<=n;i++) {
		string s;
		cin>>s;
		fill(f[i]+1,f[i]+n+1,1e9);
		for(int j=1;j<=n;j++) {
			a[i][j]=s[j-1]-'0';
			if(a[i][j]) {
				f[i][j]=1;
				if(i<j) {
					x[++tot]=i;y[tot]=j;
				}
			}
		}
		f[i][i]=0;
	}
	
	for(int k=1;k<=n;k++) {
		for(int i=1;i<=n;i++) {
			for(int j=1;j<=n;j++) {
				f[i][j]=min(f[i][j],f[i][k]+f[k][j]);
			}
		}
	}
	
	for(int i=1;i<=n;i++) {
		for(int j=1;j<=n;j++) {
			if(f[i][j]&1!=a[i][j]||f[i][j]>1e8) {
				puts("NO");
				return ;
			}
		}
	}
	
	puts("YES");
	cout<<tot<<endl;
	for(int i=1;i<=tot;i++) {
		printf("%d %d\n",x[i],y[i]);
	}
}

int main() {
	//freopen(".in","r",stdin);
	//freopen(".out","w",stdout);
	
	int t=read();
	while(t--) {
		solve();
	} 

	//fclose(stdin);
	//fclose(stdout);
	return 0;
}