JavaScript/String/CheckRearrangePalindrome.js at master · cecil-su/JavaScript · GitHub

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/**

* What is a palindrome? https://en.wikipedia.org/wiki/Palindrome

* Receives a string and returns whether it can be rearranged to become a palindrome or not

* The string can only be a palindrome if the count of ALL characters is even or if the ONLY ONE character count is odd

* Input is a string

**/

export const palindromeRearranging = (str) => {

// check that input is a string

if (typeof str !== 'string') {

return 'Not a string'

}

// Check if is a empty string

if (str.length === 0) {

return 'Empty string'

}

// First obtain the character count for each character in the string and store it in an object.

// Filter the object's values to only the odd character counts.

const charCounts = [...str].reduce((counts, char) => {

counts[char] = counts[char] ? counts[char] + 1 : 1

return counts

}, {})

// If the length of the resulting array is 0 or 1, the string can be a palindrome.

return Object.values(charCounts).filter(count => count % 2 !== 0).length <= 1

}

// testing

// > palindromeRearranging('aaeccrr')

// true

// > palindromeRearranging('leve')

// false

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