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#include <bits/stdc++.h>

using namespace std;

constexpr int LIM = 1e5;
int values[LIM + 3];
int fl[2];

void setCnt(int& k, int& l, int& m, int& best, int bc, int sv) {
    int tv, vc = sv, mc = 0, lc = 0, kc = 0;
    for(int i = 0; i <= bc; ++i) {
        tv = max(0, values[i] - 2 * vc);
        if(tv == 0)
            break;
        if(tv == 2 || tv == 1) {
            ++mc;
            ++vc;
            best += 1;
        } else if(tv == 3) {
            ++lc;
            vc += 2;
            best += 2;
        } else {
            ++kc;
            vc += 2;
            best += tv - 1;
        }
    }
    k = kc; l = lc + kc; m = l + mc;
}

int main() {
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    int t, n;
    cin >> t;
    string input;
    while(t--) {
        cin >> n >> input;
        int ci = 0, bc = -1;
        fl[0] = fl[1] = 0;
        if(input[0] == '0') {
            while(ci < n && input[ci++] == '0') {
                ++fl[0];
            }
        }
        while(ci < n) {
            if(input[ci] == '0' && input[ci - 1] == '1') {
                values[++bc] = 1;
            } else if (input[ci] == '0') {
                ++values[bc];
            }
            ++ci;
        }
        if(input[n - 1] == '0') {
            fl[1] = values[bc];
            --bc;
        }

        if(fl[1] > fl[0])
            swap(fl[1], fl[0]);

        if(bc >= 0)
            sort(values, values + bc + 1, greater<int>());

        int m, k, l, best = 0, res;

        setCnt(k, l, m, best, bc, 0);
        res = best;
        if(fl[0] >= m + k) {
            res = best + fl[0] -  m - k;
            best = 0;
            setCnt(k, l, m, best, bc, 1);
            if(fl[1] - 1 > m + k) {
                res = best + fl[0] + fl[1] - 1 - m - k;
            }
        }

        cout << n - res  << "\n";
    }
}