二分查找

//前提是查找的数组已是有序 
#include<cstdio>

//非递归 
int binary(int *arr,int low,int high,int key)
{
    while(low <= high)
    {
        int mid = (low + high) / 2;
        if(key == arr[mid])
        {
            return mid;
        }
        else if(key > arr[mid])
        {
            low = mid + 1;
        }
        else
        {
            high = mid -1;
        }
    }
    return -1;
}


//递归 
int bin_rec(int *arr, int low, int high, int key)
{
    if(low <= high)
    {
        int mid = (low + high) / 2;
        if(key == arr[mid])
        {
            return mid;
        }
        else if(key > array[mid])
        {
            bin_rec(arr,mid+1,high,key);
        }
        else
        {
            bin_rec(arr,low,mid-1,key);
        }
    }
    return -1;
 }