c语言：用二分查找算法，查找有序数组的下标

#include
int main()
{
	int arr[] = { 1,2,3,4,5,6,7,8,9 };
	int k = 7;

	int sz = sizeof(arr) / sizeof(arr[0]);
	int left = 0;
	int right = sz - 1;

	while (left<=k)
	{
		int mid = left + right / 2;
		if (arr[mid] > k)
		{
			right = mid - 1;
		}
		else if (arr[mid] < k)
		{
			left = mid - 1;
		}
		else
		{
			printf("下标是：%dn", mid);
			break;
		}
	}
	if (left > right)
	{
		printf("找不到n");
	}
	return 0;
}