leetcode: explore-strings-32 反转字符串

leetcode explore 字符串类第一题：反转字符串。相当简单的一个题目

题目分析

这里把题目贴出来：

Write a function that reverses a string. The input string is given as an array of characters char[].

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.



Example 1:

Input: ["h","e","l","l","o"]
Output: ["o","l","l","e","h"]
Example 2:

Input: ["H","a","n","n","a","h"]
Output: ["h","a","n","n","a","H"]

题意拆解：

1、输入：列表，只包括字符的列表 2、输出：列表顺序反转 3、注意事项：in-place，即O(1)的空间复杂度，也就是说不需要返回任何数据，原地修改传入的列表

参考答案

这个题目对于 Python 实现来说相当简单，因为有现成的方法可以调用。参考代码如下：

class Solution(object):
    def reverseString(self, s):
        """
        :type s: List[str]
        :rtype: None Do not return anything, modify s in-place instead.
        """
        s.reverse()

面试题引申

1、如果实现列表或者字符串反转？

s = [1, 2, 3]
# 原地修改，没有返回值
s.reverse()

# 返回新的 list
s = reversed(s)

# 特别注意切片的方式，十分灵活，也用得比较多
s = s[::-1]

2、字符串与列表的相互转换

s = [1, 2, 3]
s = "".join(s)
s = list(s)

s = "1,2,3"
s = s.split(",")

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