为什么j要再定义一次？求解~~

#include <iostream.h>
void main()
{
    int a[3][3];
    for ( int i = 0, temp = 1; i <= 2; i++)
    {
           for ( int j = 0; j <= 2; j++,temp++)
           {
               a[i][j] = temp;
               cout << a[i][j] << "  " ;
           }
           cout << endl;
    }
    cout << " After transform :" << endl;
    for ( j = 0; j <= 2; j++)       //这里不再次定义j时，会出错~~
    {
        for ( i =0 ; i <= 2; i++)
        {
            cout << a[i][j] <<"  ";
        }
        cout << endl;
    }

}