C++ :

#include<iostream>  
#include<cmath>   
#include<iostream>  
#include<cstring>  
#include<algorithm>  
using namespace std;  
int main()  
{   
	int n,m,a[100],x[1000],i;  
	cin>>n;   
	for(i=0;i<n;i++)  
	{  
		cin>>m;    
		for(int j=0;j<m;j++) cin>>a[j];         
		sort(a,a+m);          
		for(int f=0;f<m-2;f++)             
		if(a[f+1]-a[f]!=a[f+2]-a[f+1])x[i]=1;         
		if(x[i]==1)cout<<"no"<<endl;        
		else cout<<"yes"<<endl;   
	}  
	return 0;  
}