[C語言]編寫一個折半查找函數

#include <stdio.h>
int zheban(int x,int arr[],int left,int right)
{
    while(left<=right)
    {
        int mid=left-(left-right)/2;
        if(x<arr[mid])
        {
            right=mid-1;       
        }  
        else if(x>arr[mid])
        {
            left=mid+1;
        }
        else
        {
            return arr[mid];  
        }
    }
    return -1;
}
int main ()
{
    int arr[8]={1,2,3,4,5,6,7,8};
    int size=sizeof(arr)/sizeof(arr[0])-1;
    int ret=zheban(8,arr,0,size);
    if(ret==-1)
    {
        printf("not exist!"); 
    }
    else
    {
        printf("%d\n",ret);
    }
    return 0; 
     
}