输出左上角到右下角的和，为什么是输出的右上角到左下角的值啊🙏🙏

Question

#include <stdio.h>
int main()
{int n,i,j,a[100][100],sum=0;
scanf("%d",&n);
for(i=0;i<=n-1;i++)
for(j=0;j<=n-1;j++)
scanf("%d",&a[i][j]);
for(i=0;i<=n-1;i++)
for(j=n-1;j>=0;j--)
if(n-1-i==j) sum=sum+a[i][j];
printf("%d\n",sum);
return 0;
}

Answer 1

#include <stdio.h>
int main()
{
    int n, i, j, a[100][100], sum = 0;
    scanf("%d", &n);
    for (i = 0; i <= n - 1; i++)
        for (j = 0; j <= n - 1; j++)
            scanf("%d", &a[i][j]);
    for (i = 0; i <= n - 1; i++)
        sum = sum + a[i][i];
    printf("%d\n", sum);
    return 0;
}