C-(函数)二分查找

//#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>
#include<math.h>
int binary_search(int a[], int k, int s)
{
    int left = 0;
    int right = s - 1;

    while (left <= right)
    {
        int mid = (left + right) / 2;
        if (a[mid] > k)
        {
            right = mid - 1;
        }
        else if (a[mid] < k)
        {
            left = mid + 1;
        }
        else
        {
            return mid;
        }

    }
    return -1;
}
int main()
{
    int arr[] = { 1,2,3,4,5,6,7,8,9,10 };
    int key = 7;
    int sz = sizeof(arr) / sizeof(arr[0]);
    //找到了就返回找到的位置下标
    //找不到返回-1
    //数组arr传参，实际传递的不是数组本身
    //仅仅传过去了数组首元素的地址
    int ret = binary_search(arr,key,sz);
    if (-1 == ret)
    {
        printf("找不到\n");
    }
    else
    {
        printf("找到了，下标是：%d\n", ret);
    }
    return 0;
}