69-矩阵求和

#include <iostream>
using namespace std;
int main() {
    int a[103][103];
    int n;
    cin >> n;
    int ct = 1, sum = 0;
    for(int i = 1; i <= n; i++)
    	for(int j = 1; j <= n; j++)
    		a[i][j] = ct++;
	for(int i = 1; i <= n /2 + 1 ; i++){
		for(int j = n / 2 + 1 - i + 1; j <= n / 2 + 1 + i - 1; j++){
			sum += a[i][j];
			
//			cout << "ij:" << i << " " << j << " " << a[i][j] << endl;
		}
	}
	cout << "sum: " << sum << endl;
	for(int i = n / 2 + 2, k = 1; i <= n ; i++, k++){
		for(int j = k + 1; j <= n - k; j++){
			sum += a[i][j];
//			cout << "ij:" << i << " " << j << " " << a[i][j] << endl;
		}
	}
    cout << sum << endl;
    return 0;
}
/*
1   2 	3	4	5
6   7	8	9	10
11  12  13  14  15
16  17  18
*/