输出为何是27？
#include <stdio.h>
int main()
{
int arr[3][3] = {{1,2,3},{4,5,6},{7,8,9}};
int i,j;
int sum=0;
for(i=0;i<3;i++)
{
for(j=0;j<3;j++)
if(i%2==0){
if(j%2==0)
{
sum=sum+arr[i][j];
}
}
if(i%2!=0)
{
if(j%2!=0)
{
sum=sum+arr[i][j];
}
}
}
printf("对角线元素之和是：%d\n",sum);
return 0;
}
