Description
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"]
Solutions
1. Two Pointers
# Time: O(n)
# Space: O(1)
class Solution:
def reverseString(self, s: List[str]) -> None:
"""
Do not return anything, modify s in-place instead.
"""
if not s:
return
l, r = 0, len(s) - 1
while l < r:
s[l], s[r] = s[r], s[l]
l += 1
r -= 1
# return s
# 478/478 cases passed (200 ms)
# Your runtime beats 97.93 % of python3 submissions
# Your memory usage beats 98.84 % of python3 submissions (17.2 MB)