Python 线性查找与二分查找

线性查找与二分查找

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线性查找

def linear_search(li, value):
    for index, v in enumerate(li):  # 枚举，返回(index, value)
        if v == value:
            return index
    else:
        return None

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二分查找(有序列表）

def binary_search(li, value):
    left = 0                # 表头
    right = len(li) - 1     # 表尾
    while left <= right:    # 查找的区间还有值
        mid = (left + right) // 2
        if li[mid] == value:
            return value
        elif li[mid] > value:  # 需要查找的value在mid左侧
            right = mid - 1
        else:  # 需要查找的value
            left = mid + 1

    else:
        return None