题解

#include<iostream>
using namespace std;
int t,n;
string s;
bool check(string x){
	int l=0,r=0;
	for(int i =0;i<s.size();i++){
		if(s[i]!= '4' && s[i] != '7') return 0;
		if(i<s.size()/2)
		{
			l+=s[i]-'0';
		}
		else
		{
            if(s.size()%2==0 || i!= s.size()/2)
            {
            	r += s[i]-'0';
            }
			
		}
	}
    // cout << "l="<<l <<"  r==" << r << endl;
	return l == r;
}
int main(){
	cin >> t;
	while(t--){
		cin >> n;
		cin >> s;
		if(check(s)) cout << "YES"<<endl;
		else cout << "NO"<<endl;
		
	}
	return 0;
}