D_Binary_String_To_Subsequences.cpp

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

void solve() {
    int n;
    string s;
    cin >> n >> s;

    int k = 1;
    vector<int> ans(n);
    vector<int> t1, t2; // availability of 0 and 1

    for(int i=0;i<n;i++) {
        if(s[i] == '1') {
            if(t1.size()) {
                ans[i] = t1.back();
                t1.pop_back();
            }
            else {
                ans[i] = k++;
            }
            t2.push_back(ans[i]);
        }
        else {
            if(t2.size()) {
                ans[i] = t2.back();
                t2.pop_back();
            }
            else {
                ans[i] = k++;
            }
            t1.push_back(ans[i]);
        }
    }

    cout << k - 1 << "\n";
    for(auto i : ans) cout << i << " ";
    cout << "\n";


}


int32_t main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    int _;
    cin >> _;
    while (_-->0) {
        solve();
    }

    return 0;
}