[344] Reverse String

https://leetcode.com/problems/reverse-string/description/

• algorithms
• Easy (61.90%)
• Source Code: 344.reverse-string.py
• Total Accepted: 405.6K
• Total Submissions: 643K
• Testcase Example: '["h","e","l","l","o"]'

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"]

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

        lens = len(s)
        i, j = 0, lens-1
        while i < j:
            s[i], s[j] = s[j], s[i]
            i += 1
            j -= 1

        return