O(1)求解答案即可

总时间复杂度 O(n^2)

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, m;
    cin >> n >> m;
    vector<vector<char>> c(n + 1, vector<char>(n + 1));
    for (int i = 1; i <= n; ++i) {
        string s;
        cin >> s;
        for (int j = 1; j <= n; ++j) {
            c[i][j] = s[j - 1];
        }
    }
    int x = 0, y = 0;
    for (int i = 1; i <= n; ++i) {
        string t;
        cin >> t;
        for (int j = 1; j <= n; ++j) {
            if (t[j - 1] != c[i][j]) {
                x = i;
                y = j;
            }
        }
    }
    int l1 = max(1, x - m + 1);
    int l2 = min(x, n - m + 1);
    int r1 = max(1, y - m + 1);
    int r2 = min(y, n - m + 1);
    long ans = (r2 - r1 + 1) * (l2 - l1 + 1);
    cout << ans << endl;
    return 0;
}