JavaScript/String/IsPalindrome.js at master · TheAlgorithms/JavaScript · GitHub

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/**

* @function isPalindromeIterative

* @description isPalindromeIterative function checks whether the provided input is palindrome or not

* @param {String | Number} x - The input to check

* @return {boolean} - Input is palindrome or not

* @see [Palindrome](https://en.wikipedia.org/wiki/Palindrome)

* Big-O Analysis

* Time Complexity

- O(N) on average and worst case scenario as input is traversed in linear fashion

- O(1) on best case scenario if the input already is a string (otherwise toString() method takes O(N))

and the first & last characters don't match, triggering an early return

* Space Complexity

- O(1)

export function isPalindromeIterative(x) {

if (typeof x !== 'string' && typeof x !== 'number') {

throw new TypeError('Input must be a string or a number')

}

// Convert x to string whether it's number or string

const string = x.toString()

const length = string.length

if (length === 1) return true

// Apply two pointers technique to compare first and last elements on each iteration

for (let start = 0, end = length - 1; start < end; start++, end--) {

// Early return if compared items are different, input is not a palindrome

if (string[start] !== string[end]) return false

}

// If early return in condition inside for loop is not reached, then input is palindrome

return true

}

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