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

Example:

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

class Solution {

    public String reverseString(String s) {

        char[] ch = s.toCharArray();

        int start = 0;

        int end = s.length() - 1;

        while (start < end) {

            char temp = ch[start];

            ch[start] = ch[end];

            ch[end] = temp;

            start++;

            end--;

        }

        return new String(ch);

    }

}