#define _CRT_SECURE_NO_WARNINGS 1

#include <stdio.h>

int binary_search(int arr[], int key, int left, int right)
{
   int mid = 0;
 while(left <= right)
{
	mid = left - ((left - right)>>1);
	if(arr[mid] > key)
	{
		right = mid - 1;
	}
	else if(arr[mid] < key)
	{
		left = mid +1;
	}
	else
	{
        return mid;
	}
}
  if(left > right)
  {
	  return -1;
  }
  return 0;
}
 

int main()
{
	int arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
	int key = 6;
	int ret = binary_search(arr, key, 2, 8);
	if(ret != -1)
	{
		printf("找到了！下標為：%d\n",ret);
	}
	else
	{
		printf("不存在！\n");
	}
	return 0;
}