How to reverse a string given a char array

Question

I am trying a leetcode question on reversing the string. I don't understand why my solution is not working. Can anyone code review it please?

class Solution {
    public char[] reverseString(char[] s) {
        char[] temp = new char[s.length];

        int index = s.length - 1;

        for (int i = 0; i < s.length; ++i){
            temp[i] = s[index--];
        }

        return temp;
    }
}

Leetcode says my output is ["h", "e", "l", "l", "o"] when the output should be ["o", "l", "l", "e", "h"]. Thanks for the help.

works for me assuming that s == 'hello'

Scary Wombat
– Scary Wombat

2020-02-05 02:55:35 +00:00
Commented Feb 5, 2020 at 2:55 — Scary Wombat
– Scary Wombat, Commented Feb 5, 2020 at 2:55

Elliott Frisch · Accepted Answer · 2020-02-05 02:55:49Z

2

Your solution does return an array with the characters in reverse order, but it would appear they assume you will do it in-place (and test accordingly). Iterate half of the array, and swap the current character with the index offset from the length. Like,

public char[] reverseString(char[] s) {
    for (int i = 0; i < s.length / 2; ++i) {
        char temp = s[i];
        s[i] = s[s.length - i - 1];
        s[s.length - i - 1] = temp;
    }
    return s;
}

If that is not correct, please carefully review all of the requirements posted (and share them here).

answered Feb 5, 2020 at 2:55

Elliott Frisch

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