题解 | 弹地小球

#include <iostream>
#include <iomanip>

using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(2);
    int m, n;
    double H;
    while (cin >> m) {
        for (int i = 0; i < m; i++) {
            cin >> H >> n;
            if (n == 0) {
                cout << 0.00 << "\n";
                continue;
            } else if (n == 1) {
                cout << H << "\n";
                continue;
            }
            double sum = H;
            for (int j = 1; j < n; j++) {
                sum += H;
                H = H / 2;
            }
            cout << sum << "\n";
        }
        return 0;
    }
}