#include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(nullptr);     cout.tie(nullptr);     long long t;     cin >> t;     while (t--) {       vector<vector<long long> > a(2);       vector<long long> ans;       long long n;       string b;       cin >> n >> b;       long long cou = 1;       for (char c : b) {         long long x = c -  0 ;         if (a[x].size() == 0) a[x].push_back(cou++);         ans.push_back(a[x].back());         a[!x].push_back(a[x].back());         a[x].pop_back();       }       cout << cou - 1 <<   n ;       for (long long i : ans) cout << i <<    ;       cout <<   n ;     }     return 0;   }   