Coding problem · Easy · Basics

Reverse a String

Easy Algorithms & data structures

Given a string s, return it reversed.

"hello" becomes "olleh".

Example 1

Input: s = "hello"
Output: "olleh"

Example 2

Input: s = "ReadyCamel"
Output: "lemaCydaeR"

Hints

Hint 1

Build a new string by reading the characters from the last one to the first.

Hint 2

Most languages can split a string into characters, reverse the list and join it back.

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Solution and explanation

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Time O(n) · Space O(n)

Walk from the end to the start, or use the language's built-in reverse on a list of characters. Strings are immutable in most languages, so we build a new one.

Reference solution

function reverseString(s) {
  return s.split('').reverse().join('');
}

function reverseString(s: string): string {
  return s.split('').reverse().join('');
}

def reverse_string(s: str) -> str:
    return s[::-1]

<?php

function reverseString(string $s): string
{
    return strrev($s);
}

class Solution {
    public String reverseString(String s) {
        return new StringBuilder(s).reverse().toString();
    }
}

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