二分查找和快速排序

#include <stdio.h>
void output(int *arr,int n)
{
    for(int i=0;i<n;i++)
    {
        printf("%d\t",arr[i]);
    }
    puts("");
}
void half_search(int *arr,int n,int key)
{
    int high=n-1;
    int low=0;
    int mid;
    while(low<=high)
    {
        mid=(high+low)/2;
        if(arr[mid]<key)
        {
            low=mid+1;
        }
        else if(arr[mid]>key)
        {
            high=mid-1;
        }
        else if(arr[mid]==key)
        {
            printf("mid=%d\n",mid);
            return;
        }
    }
    puts("half_sort error");
    return;
}
int fun(int *arr,int low,int high)
{
    int key=arr[low];
    while(low<high)
    {
        while(low<high&&key<=arr[high])
        {
            high--;
        }
        arr[low]=arr[high];
        while(low<high&& key>=arr[low])
        {
            low++;
        }
        arr[high]=arr[low];
    }
    arr[low]=key;
    return low;
}
void fast_sort(int *arr,int low,int high)
{
    if(low>=high)
    {
        return;
    }
    int mid= fun(arr,low,high);
    fast_sort(arr,low,mid-1);
    fast_sort(arr,mid+1,high);
}
int main() {
    int n;
    printf("please input n:");
    scanf("%d",&n);
    int arr[n];
    for(int i=0;i<n;i++)
     {
       printf("arr[%d]=",i);
       scanf("%d",&arr[i]);
     }
    output(arr,n);
    int key;
    printf("input sort key:");
    scanf("%d",&key);
    half_search(arr,n,key);
    int low=0;
    int high=n-1;
    fast_sort(arr,low,high);
    puts("after fast_sort:");
    output(arr,n);
    return 0;
}