Forest density

#include <bits/stdc++.h>
 
using namespace std;
 
signed main() {
    
    int n, q; // forest size, query number
    cin >> n >> q;
    
    int forest[n+1][n+1];
    
    // get input && calc prefix sum
    for (int i = 1; i <= n; i++) {
 
        for (int j = 1; j <= n; j++) {
            char input;
            cin >> input;
            if (input == '.') forest[i][j] = forest[i][j-1];
            else forest[i][j] = forest[i][j-1] + 1;
        }
    }
 
    // handle queries
    for (int i = 0; i < q; i++) {
        int x1, x2, y1, y2;
        cin >> y1 >> x1 >> y2 >> x2;
 
        int num_rows = y2 - y1; 
        int sum = 0;
        for (int j = 0; j <= num_rows; j++) {
            sum += forest[y1+j][x2] - forest[y1+j][x1-1]; 
        }
        cout << sum << "\n";
    }
 
    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED