Good afternoon! Here's our prompt for today.

We're given a string that's a mixture of several alphabetical characters.

1const str = "algototheehtotdaily";

Could you write a method to find the longest substring that is considered a palindrome? In the above example, it would be "totheehtot".

Where there are multiple longest palindromic substrings of the same length, for example in "abracadabra" ("aca" and "ada"), return the first to appear.

Constraints

• The string can be empty, in which case return an empty string
• The string will consist of only lowercase alphabets
• Expected time complexity : O(n^2)
• Expected space complexity : O(n^2)

Try to solve this here or in Interactive Mode.

How do I practice this challenge?

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    'PASSED: ' + "`longestPalindrome('nasduhuuhdousan')` should return `'huuh'`"

var assert = require('assert');

​

const longestPalindrome = (str) => {

  // fill in

  return '';

};

​

try {

  assert.equal(longestPalindrome(''), '');

​

  console.log('PASSED: ' + "`longestPalindrome('')` should return `''`");

} catch (err) {

  console.log(err);

}

​

try {

  assert.equal(longestPalindrome('algodaily'), 'a');

​

  console.log(

    'PASSED: ' + "`longestPalindrome('algodaily')` should return `'a'`"

  );

} catch (err) {

  console.log(err);

}

​

try {

  assert.equal(longestPalindrome('gymmyg'), 'gymmyg');

​

  console.log(

Here's our guided, illustrated walk-through.

How do I use this guide?