代码:
#include<bits/stdc++.h>
using namespace std;
int main(){
int T;
cin>>T;
while(T--){
int e=0,f=0;
int n;
cin>>n;
string a;
cin>>a;
for(int i = 0;i < n;i++){
if(a[i]=='2'||a[i]=='3') f++;
if(a[i]=='0'&&e!=0) e--;f++;
if(a[i]=='1') e++;
}
cout<<f+e/2<<endl;
}
}