00-自测2. 素数对猜想

#include <stdio.h>
#include <math.h>

int sushu[10000] ;
int counter = 0 ;

void initArray ( int num )
{
    int flag = 0 ;

    for ( int i = 2 ; i < num ; i++ )
    {
        flag = 1 ;

        for ( int j = 2 ; j <= (int)sqrt(i*1.0) ; j++ )
        {
            if ( i % j == 0 )
            {
                flag = 0 ;
                break ;
            }

        }
        if ( flag )
        {
            sushu[counter++] = i ;
        }
    }
}

int main ( void )
{
    int num ;
    int pcounter = 0 ;

    scanf ("%d" , &num ) ;

    initArray (num) ;

    for ( int i = counter-1 ; i >0 ; i-- )
    {
            int j = i-1 ;

            if ( (sushu[i] - sushu[j]) == 2 )
            {
                pcounter++ ;
            }

    }


    printf("%d" , pcounter) ;
    return 0 ;
}

差一个测试点