CPP0237 - MA TRẬN VUÔNG LỚN NHẤT

#include <iostream>
using namespace std;
int findSubSquare(char mat[][100],int N)
{
    int max = 0; 
    int hor[100][100], ver[100][100];
    hor[0][0] = ver[0][0] = (mat[0][0] == 'X');
    for (int i = 0; i < N; i++)
    {
        for (int j = 0; j < N; j++)
        {
            if (mat[i][j] == 'O')
                ver[i][j] = hor[i][j] = 0;
            else
            {
                hor[i][j]
                    = (j == 0) ? 1 : hor[i][j - 1] + 1;
                ver[i][j]
                    = (i == 0) ? 1 : ver[i - 1][j] + 1;
            }
        }
    }

    for (int i = N - 1; i >= 1; i--)
    {
        for (int j = N - 1; j >= 1; j--)
        {
            int small = min(hor[i][j], ver[i][j]);
            while (small > max)
            {
                if (ver[i][j - small + 1] >= small
                    && hor[i - small + 1][j] >= small)
                {
                    max = small;
                }
                small--;
            }
        }
    }
    return max;
}
int main()
{
    int t; cin >> t;
    while (t--) {
        int n; cin >> n;
        char M[100][100];
        for (int i = 0; i < n; i++)for (int j = 0; j < n; j++)cin >> M[i][j];
        cout << findSubSquare(M, n) << endl;;
    }
    return 0;
}