Forest density

#include <iostream>
#include <vector>

using namespace std;

int main() {
    long long n, q;
    cin >> n >> q;

    vector<vector<char>> v(n, vector<char>(n));
    vector<vector<long long>> pre(n, vector<long long>(n));

    for (long long i = 0; i < n; ++i) {
        for (long long j = 0; j < n; ++j) {
            cin >> v[i][j];
            if (i == 0 and j == 0)
                pre[i][j] = 0;
            else if (i == 0)
                pre[i][j] = pre[i][j - 1];
            else if (j == 0)
                pre[i][j] = pre[i - 1][j];
            else {
                pre[i][j] = pre[i - 1][j] + pre[i][j - 1] - pre[i - 1][j - 1];
            }
            if (v[i][j] == '*')
                ++pre[i][j];
        }
    }

    for (long long i = 0; i < q; ++i) {
        long long y1, x1, y2, x2;
        cin >> y1 >> x1 >> y2 >> x2;

        int val1, val2, val3, val4;
        if (y2-1 < 0 or x2-1 < 0)
            val1 = 0;
        else
            val1 = pre[y2 - 1][x2 - 1];
        if (y1-2 < 0 or x2-1 < 0)
            val2 = 0;
        else
            val2 = pre[y1 - 2][x2 - 1];
        if (y2 - 1 < 0 or x1-2 < 0)
            val3 = 0;
        else
            val3 = pre[y2 - 1][x1 - 2];
        if (y1-2 < 0 or x1-2 < 0)
            val4 = 0;
        else
            val4 = pre[y1 - 2][x1 - 2];
        cout << val1 - val2 - val3 +  val4 << endl;
    }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED