ab_flipping(greedy).cpp

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

#define faster_ayman    ios_base::sync_with_stdio(false);cin.tie(NULL);
#define int             long long
#define pb              push_back
#define rep(i, a, b)    for (auto i = a; i < b; i++)
#define all(a)          (a).begin(), (a).end()
#define testcase        int tt;cin >> tt;while (tt--)
#define inf             1e18

typedef vector<int>                         vi;
typedef vector<pair<int,int>>               vp;
typedef vector<double>                      vd;
typedef vector<char>                        vc;
typedef set<int>                            si;
typedef set<char>                           sc;
typedef unordered_set<int>                  usi;

void solve() {
    int n;              cin >> n;
    string s;           cin >> s;
    int prothom_a = inf, last_b = 0;
    rep(i, 0ll, n) {
        if (s[i] == 'A') {
            prothom_a = min(prothom_a, i);
        }else {
            last_b = i;
        }
    }
    cout << max(0ll, last_b - prothom_a) << '\n';
}

signed main() {
    
    faster_ayman
    testcase {
        solve();
    }
    
    return 0;
}