题解，但是正常思路

#include <cstdio>
#include <iostream>

using namespace std;



int main() {
    long long n, m, k;
    cin >> n >> m >> k;
    long long a[n+10][m+10];
	long long b[n+10][m+10];
	long long res[n+10][m+10];
    for (long long i = 1; i <= n; i++) {
    	for (long long j = 1; j <= m; j++) {
    		cin >> a[i][j];
		}
	}
    for (long long i = 1; i <= m; i++) {
    	for (long long j = 1; j <= k; j++) {
    		cin >> b[i][j];
		}
	}
	
	for (long long i = 1; i <= n; i++) {
		for (long long j = 1; j <= k; j++) {
			long long ans = 0;
			for (long long s = 1; s <= m; s++) {
				ans += a[i][s] * b[s][j];
			}
			res[i][j] = ans;
		}
	}
    
    for (long long i = 1; i <= n; i++) {
    	for (long long j = 1; j <= k; j++) {
    		cout << res[i][j] << " ";
		}
		cout << endl;
	}
    return 0;
}

终于等到你，还好我没放弃……