顺序查找

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def seq_search(items, key):
    """顺序查找"""
    for index, item in enumerate(items):
        if item == key:
            return index
     return -1

折半查找

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def bin_search(items, key):
    """折半查找"""
    start, end = 0, len(items) - 1
    while start <= end:
        mid = (start + end) // 2
        if key > items[mid]:
            start = mid + 1
            elif key < items[mid]:
                end = mid - 1
                else:
                    return mid
    return -1