二分查找，递归

#include<stdio.h>
#include <iostream>
int a[10] = {1,2,3,4,5,6,7,8,9,10};



int binarySearch(int left,int right,int key)
{
    int middle = (left+right)/2;

   if(middle >= right && middle <= left)
        return -1;
    if(a[middle] == key)
        return middle;
    else if(a[middle] > key)
    {
        binarySearch(left,middle-1,key);
    }
    else
    {
        binarySearch(middle+1,right,key);
    }
}
int main()
{
    std::cout << binarySearch(0,9,2) << std::endl;
}