我的二分查找法（递归）

//经典的二分查找法写法
template <typename T>
int binary_search(T *array, int n, T value)
{
	if(array == NULL) //判断array是否为空指针
	{
		cout << "input array is NULL." << endl;
		return -1;
	}
	int left = 0, right = n-1;
	while(left <= right)
	{
		int middle = left + ((right - left)>>1);	//用右移操作代替除2，提高效率
		if(array[middle] > value)
		{
			right = middle - 1;
		}
		else if(array[middle] < value)
		{
			left = middle + 1;
		}
		else
			return middle;
	}
	return -1;
}


//我写的二分查找法，测试过也没有错误，递归的效率可能低了些
template <typename T>
int binarySearch(T *array,int left, int right, T num)
{
	assert(array != NULL);
	int mid = left + (right - left)/2;
	if(num == array[mid])
		return mid;
	else if(num < array[mid])
		right = mid - 1;
	else
		left = mid + 1;
	if(left > right)
		return -1;
	return binarySearch(array, left, right, num);
}

int main()
{
	int a[]={4,4,5,6,7,7,9,42};  

	cout<<binarySearch(a,0,sizeof(a)/sizeof(int),9)<<endl;  
	system("pause");
	return 0;
}

转载于:https://www.cnblogs.com/cnsec/p/3789806.html