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GitHub Repository: jackfrued/Python-100-Days
 Path: blob/master/Day01-15/code/Day12/str2.py
Views: 729
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"""

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字符串常用操作 - 实现字符串倒转的方法

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Version: 0.1

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Author: 骆昊

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Date: 2018-03-19

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"""

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from io import StringIO

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def reverse_str1(str):

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    return str[::-1]

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def reverse_str2(str):

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    if len(str) <= 1:

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        return str

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    return reverse_str2(str[1:]) + str[0:1]

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def reverse_str3(str):

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    # StringIO对象是Python中的可变字符串

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    # 不应该使用不变字符串做字符串连接操作 因为会产生很多无用字符串对象

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    rstr = StringIO()

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    str_len = len(str)

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    for index in range(str_len - 1, -1, -1):

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        rstr.write(str[index])

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    return rstr.getvalue()

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def reverse_str4(str):

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    return ''.join(str[index] for index in range(len(str) - 1, -1, -1))

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def reverse_str5(str):

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    # 将字符串处理成列表

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    str_list = list(str)

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    str_len = len(str)

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    # 使用zip函数将两个序列合并成一个产生元组的迭代器

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    # 每次正好可以取到一前一后两个下标来实现元素的交换

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    for i, j in zip(range(str_len // 2), range(str_len - 1, str_len // 2, -1)):

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        str_list[i], str_list[j] = str_list[j], str_list[i]

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    # 将列表元素连接成字符串

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    return ''.join(str_list)

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if __name__ == '__main__':

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    str = 'I love Python'

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    print(reverse_str1(str))

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    print(str)

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    print(reverse_str2(str))

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    print(str)

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    print(reverse_str3(str))

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    print(str)

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    print(reverse_str4(str))

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    print(str)

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    print(reverse_str5(str))

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    print(str)

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