1181C - Flag - CodeForces Solution

#include <bits/stdc++.h>

using namespace std;
using i64 = long long;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    cout.setf(ios::fixed), cout.precision(8);

    int n, m;
    cin >> n >> m;

    vector<string> g(n);
    for (int i = 0; i < n; i++) {
        cin >> g[i];
    }

    vector<vector<int>> c(n, vector<int>(m, 1));
    for (int i = n - 2; i >= 0; i--) {
        for (int j = 0; j < m; j++) {
            if (g[i][j] == g[i + 1][j]) {
                c[i][j] = c[i + 1][j] + 1;
            }
        }
    }

    i64 ans = 0;
    for (int i = 0; i < n; i++) {
        for (int j = 0, k = 0; j < m; j++, ans += k) {
            int h = c[i][j];
            if (i + 3 * h <= n && c[i + h][j] == h && c[i + h * 2][j] >= h) {
                if (j > 0 && c[i][j - 1] == c[i][j] && g[i][j - 1] == g[i][j] && g[i + h][j - 1] == g[i + h][j] && g[i + 2 * h][j - 1] == g[i + 2 * h][j]) k++;
                else k = 1;
            } else {
                k = 0;
            }
        }
    }

    cout << ans;

    return 0;
}