LeetCode 344. Reverse String



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"]


Keep swapping one character from the beginning and one character from the end.

Python Solution

class Solution:
    def reverseString(self, s: List[str]) -> None:
        Do not return anything, modify s in-place instead.
        i = 0
        j = len(s) - 1
        while (i < j):
            temp = s[i]
            s[i] = s[j]
            s[j] = temp
            i = i + 1
            j = j - 1
  • Time complexity: O(N)
  • Space complexity: O(1)

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