折半查找递归和非递归实现

//递归
int BinarySearch(int arr[],int n,int left, int right)
{
	if (left <= right)
	{
		int middle = left + (right - left)/2; //防溢出

		if (n == arr[middle])
		{
			return middle;
		}
		else if (n < arr[middle])
		{
			return BinarySearch(arr,n,left,middle - 1);
		}
		else
		{
			return BinarySearch(arr,n,middle + 1,right);
		}
	}

	return -1;
}

//非递归
int BinarySearch(int arr[],int n,int length)
{
	int left = 0;
	int right = length - 1;
	int middle = 0;

	while (left <= right)
	{
		middle = left + (right - left)/2;
		if (arr[middle] == n)
		{
			return middle;
		}
		else if (n < arr[middle])
		{
			right = middle - 1;
		}
		else
		{
			left = middle + 1;
		}
	}

	return -1;
}