改错 求对角线元素之和并输出矩阵

#include<stdio.h>
#define N 3
void main()
{
float a[N][N];
int i,j;
float sum=0;
printf("Please input a rectangle element:\n");
for(i=0;i<N;i++)
for(j=0;j<N;j++)
scanf("%f",&a[i][j]);
printf("The rectangle is:");
for(i=0;i<N;i++)
for(j=0;j<N;j++)
{
printf("%f",a[i][j]);
if(j>N-2)
printf("\n");
}
for(i=0;i<N;i++)
sum+=a[i][i];
printf("duijiaoxiao he is:sum=%f",sum);
}
错误在哪儿
请大虾指点
赐教！
----------------解决方案--------------------------------------------------------
#include<iostream.h>
#define N 3
void main()
{
float a[N][N];
int i,j;
float sum=0;
cout<<"Please input a rectangle element:";
for(i=0;i<N;i++)
{
for(j=0;j<N;j++)
{
cin>>a[i][j];
}
}
cout<<"The rectangle is:"<<endl;
for(i=0;i<N;i++)
{
for(j=0;j<N;j++)
{
cout<<a[i][j];
}
cout<<endl;
}
for(i=0;i<N;i++)
sum+=a[i][i];
cout<<sum;
}

----------------解决方案--------------------------------------------------------
#include<stdio.h>
#define N 3
void main()
{
float a[N][N];
int i,j;
float sum=0;
printf("Please input a rectangle element:\n");
for(i=0;i<N;i++)
{
for(j=0;j<N;j++)
{
scanf("%f",&a[i][j]);
printf("%f",a[i][j]);
}
printf("\n");
}

for(i=0;i<N;i++)
for(j=0;j<N;j++)
if(i==j||(i+j)==(N-1))
sum+=a[i][J];
printf("duijiaoxiao he is:sum=%f",sum);
}

----------------解决方案--------------------------------------------------------