求一个3×3矩阵对角线元素之和

/求一个3×3矩阵对角线元素之和。/

#include <stdio.h>

int main(void)
{
    int matrix[3][3] = {{1, 2, 3},
                        {4, 5, 6},
                        {7, 8, 9}};
    int sum = 0;
    for (int i = 0; i < 3; i++)
    {
        sum += matrix[i][i];
    }
    printf("and %d\n", sum);
    return 0;
}