two pointers October 1, 2022

Reverse string

Time O(n) Space O(1) Open original problem

We will take 2 pointers, one at the beginning and one at the end of the string. Then we swap their position and move to the next character. Once these two pointers meet, we stop.

class Solution:
    def reverseString(self, s: List[str]) -> None:
        l, r = 0, len(s)-1
        while l<=r:
            s[l], s[r] = s[r], s[l]
            l += 1
            r -= 1

Time Complexity: O(n)
Space Complexity: O(1)