包含了二分查找的两种写法（左闭右闭和左闭右开）

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"""
题目描述：
给定数组nums = [1, 3, 6, 8, 9, 12, 16, 19, 20]

target = 6
若数组中包含target，则返回数组下标，否则返回-1
"""

def binary_search_1(nums, target):
    """左闭右闭区间的二分搜索写法"""
    left, right = 0, len(nums) - 1

    while left <= right:
        middle = left + (right - left) // 2

        if nums[middle] > target:
            right = middle - 1
        elif nums[middle] < target:
            left = middle + 1
        else:
            return middle
    return -1

def binary_search_2(nums, target):
    """左闭右开区间的写法"""
    left, right = 0, len(nums)

    while left < right:
        middle = left + (right - left) // 2

        if nums[middle] > target:
            right = middle
        elif nums[middle] < target:
            left = middle + 1
        else:
            return middle
    return -1

if __name__ == "__main__":
    nums = [1, 3, 6, 8, 9, 12, 16, 19, 20]
    target = 6
    # 注意使用二分法的前提是数组必须是有序的
    nums.sort()

    print(binary_search_1(nums, target))
    print(binary_search_2(nums, target))

"""
输出结果为：
2
2
"""