344-reverse-string

Question

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

Write a function that takes a string as input and returns the string reversed.

Example:

Given s = "hello", return "olleh".

Thought Process

1. Two Pointers
   1. Use two pointer to track the start and end of string
   2. Swap the character at each pointer and then shrink toward the center
   3. Time complexity O(n)
   4. Space complexity O(1)

Solution

class Solution {
    public String reverseString(String s) {
        char[] chars = s.toCharArray();
        int i = 0, j = chars.length - 1;
        while (i < j) swap(chars, i++, j--);
        return String.valueOf(chars);
    }

    private void swap(char[] chars, int i, int j) {
        char tmp = chars[i];
        chars[i] = chars[j];
        chars[j] = tmp;
    }
}

Additional