用c语言分别写出n阶方阵a的主对角线元素和，副对角线元素之和，非对角线元素之和

下面是用 C 语言实现的代码：

#include <stdio.h>

int main()
{
    int a[10][10], i, j, n, sum1 = 0, sum2 = 0, sum3 = 0;

    printf("Enter the order of matrix: ");
    scanf("%d", &n);

    printf("Enter the elements of matrix:\n");
    for(i = 0; i < n; i++)
    {
        for(j = 0; j < n; j++)
        {
            scanf("%d", &a[i][j]);
        }
    }

    // 计算主对角线元素之和
    for(i = 0; i < n; i++)
    {
        sum1 += a[i][i];
    }

    // 计算副对角线元素之和
    for(i = 0, j = n - 1; i < n && j >= 0; i++, j--)
    {
        sum2 += a[i][j];
    }

    // 计算非对角线元素之和
    for(i = 0; i < n; i++)
    {
        for(j = 0; j < n; j++)
        {
            if(i != j && i + j != n - 1)
            {
                sum3 += a[i][j];
            }
        }
    }

    printf("Sum of main diagonal elements: %d\n", sum1);
    printf("Sum of secondary diagonal elements: %d\n", sum2);
    printf("Sum of non-diagonal elements: %d\n", sum3);

    return 0;
}

假设输入的方阵为：

1 2 3
4 5 6
7 8 9

则输出结果为：

Enter the order of matrix: 3
Enter the elements of matrix:
1 2 3
4 5 6
7 8 9
Sum of main diagonal elements: 15
Sum of secondary diagonal elements: 15
Sum of non-diagonal elements: 28