二分查找的递归和非递归实现

二分查找的递归和非递归实现

递归实现：

//时间复杂度：O(logN)
//空间复杂度：O(logN)
int BinSearch(int arr[], int left, int right, int key)   //递归实现二分查找
{
	if (left <= right)
	{
		int mid = (left + right) / 2;
		if (arr[mid] == key)
		{
			return mid;
		}
		if (arr[mid] > key)
		{
			return BinSearch(arr, left, mid - 1, key);
		}
		if (arr[mid] < key)
		{
			return BinSearch(arr, mid + 1, right, key);
		}
	}
	return -1;	
}

非递归实现：

//时间复杂度：O(logN)
//空间复杂度：O(1)
int BinSearch(int arr[], int SizeOfArr, int key)   //非递归实现
{
	int left = 0;
	int right = SizeOfArr - 1;
	int mid = 0;
	while (left <= right)
	{
		mid = (left + right) / 2;
		if (arr[mid] == key)
		{
			return mid;
		}
		if (arr[mid] > key)
		{
			right = mid - 1;
		}
		else if (arr[mid] < key)
		{
			left = mid + 1;
		}
	}
	return -1;
}