Forest density

#include <iostream>
#include <vector>

using namespace std;

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

    int n, q;
    cin >> n >> q;

    vector<vector<int>> prefixSum(n + 1, vector<int>(n + 1, 0));

    for (int i = 1; i <= n; i++) {
        string row;
        cin >> row;
        for (int j = 1; j <= n; j++) {
            prefixSum[i][j] = (row[j - 1] == '*' ? 1 : 0) + 
                              prefixSum[i - 1][j] + 
                              prefixSum[i][j - 1] - 
                              prefixSum[i - 1][j - 1];
        }
    }

    while (q--) {
        int y1, x1, y2, x2;
        cin >> y1 >> x1 >> y2 >> x2;

        int treeCount = prefixSum[y2][x2] - 
                        prefixSum[y1 - 1][x2] - 
                        prefixSum[y2][x1 - 1] + 
                        prefixSum[y1 - 1][x1 - 1];

        cout << treeCount << '\n';
    }

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED