程序代码：

#include <stdio.h>

int main()
{
    int arr[8]={21,24,7,9,40,25,6,90};
    int i,j,tmp;
    for(i=0;i<8;i++)
    {
        for(j=i+1;j<8;j++)
        {
            if(arr[i]<arr[j])
            {
                tmp=arr[i];
                arr[i]=arr[j];
                arr[j]=tmp;
            }
        }
    }
    int b=23;
    for(i=0;i<8;i++)
    {
        if(arr[i]<=b) break;
    }
    printf("小于本身最大值是%4d   大于本身最小值是%4d\n",arr[i],arr[i-1]);
    return 0;
}

程序代码：

#include <stdio.h>

void foo( int arr[], size_t n, int value, int** restrict pless, int** restrict pgreater )
{
    *pless=NULL, *pgreater=NULL;
    for( size_t i=0; i!=n; ++i )
    {
        if( arr[i] < value )
        {
            if( !*pless || arr[i]>**pless )
                *pless = &arr[i];
        }
        else if( arr[i] > value )
        {
            if( !*pgreater || arr[i]<**pgreater )
                *pgreater = &arr[i];
        }
    }
}

int main( void )
{
    int Array[8] = { 1,4,7,9,40,23,6,90 };

    int *pless, *pgreater;
    foo( Array, sizeof(Array)/sizeof(Array[0]), 11, &pless, &pgreater );
    if( pless )
        printf( "%d\n", *pless );
    if( pgreater )
        printf( "%d\n", *pgreater );

    return 0;
}

程序代码：

#include <stdio.h> 
void main()
{
    int i,c=11,limax,lamin,a[]={1,4,7,9,40,23,6,90};
    for(i=0,limax=lamin=a[0];i<8;i++)
    {
        if((a[i]>c&&a[i]<lamin)||lamin<c)lamin=a[i];
        if((a[i]<c&&a[i]>limax)||limax>c)limax=a[i];
    }
    printf("紧挨着%d的两个数是%d,%d\n",c,limax,lamin);
}