C语言：编写折半查找函数，即二分法

#include<stdio.h>
#include <stdlib.h>
int main()
{
     int ret=0;
     int arr[]={1,2,5,6,88,99,456,666};
     ret= binsearch(666,arr,0,sizeof(arr) / sizeof(arr[0])-1);
    if(ret!=-1)
   {
       printf("%d",ret);  
    }
   else
   {
      printf("not exist"); 
   }
 return 0;
}

int binsearch(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;
}