Forest density

#include <iostream>
#include <vector>

using namespace std;

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

    vector<vector<char>> mat(n, vector<char>(n));
    for (int i=0;i<n;i++){
        for (int j=0;j<n;j++){
            
            cin>> mat[i][j];
        }
    }

    vector<vector<int>> queries(q, vector<int>(4));
    for (int i=0;i<q;i++){
        cin >> queries[i][0] >> queries[i][1] >> queries[i][2] >> queries[i][3];
    }

    vector<vector<int>> trees(n, vector<int>(n));
    for (int i=0;i<n;i++){
        for (int j=0;j<n;j++){
            int tree=mat[i][j]=='*';
            if (i>0){
                tree+=trees[i-1][j];
            }
            if (j>0){
                tree+=trees[i][j-1];
            }

            if (i>0 && j>0){
                tree-=trees[i-1][j-1];
            }
            trees[i][j]=tree;
            //cout << trees[i][j];
        }
        //cout << '\n';
    }
    for (auto &q: queries){
        vector<int> coord1={min(q[0],q[2])-2, min(q[1],q[3])-2};
        vector<int> coord2={max(q[0],q[2])-1, max(q[1],q[3])-1};
        /*
        for (int i: coord1){
            cout << i << ' ';
        }
        for (int i: coord2){
            cout << i << '\n';
        }
        */
        int val1=trees[coord2[0]][coord2[1]];
        //cout << "B";
        int val2=coord1[0]>=0 ? trees[coord1[0]][coord2[1]] : 0;

        //cout << "C";
        int val3=coord1[1]>=0 ? trees[coord2[0]][coord1[1]] : 0;
        //cout << "D";
        int val4=0;
        if (coord1[0]>=0){
            if (coord1[1]>=0){
                val4=trees[coord1[0]][coord1[1]];
            } 
        }

        //cout << "E\n";
        cout << val1-val2-val3+val4<<'\n';
    }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED