Day1 of the #100DaysOfAlgorithms Palindrome Checker

Photo by VD Photography on Unsplash

Write a function that takes a string as input and checks if it is a palindrome.

A palindrome is a word, phrase, number, or another sequence of characters that reads the same backward or forward (ignoring spaces, punctuation, and capitalization).

Solution

Characteristics of a palindrome

1. The first letter is equal to the last letter
2. The second letter is equal to the last second letter
3. Compare the first nth letter to the last nth letter
4. A single character is not a palindrome
5. An empty string is not a palindrome
6. A palindrome does not contain special characters
7. A palindrome can contain a number

Code

function compareChar(firstChar: string, lastChar: string): boolean {
  return firstChar === lastChar ? true : false
}

function isPolindrome(input: string): any {
  let isPolindrome: boolean = true
  if (input === '') {
   isPolindrome = false
  } else {
    let newInput: any = input.replace(/[^a-zA-Z0-9]/g, '').toLowerCase()
    let textArr: any[] = newInput.split('')
    let arrySize: number = textArr.length
    if(arrySize === 1){
      isPolindrome = false
    }else{
      for (let i = 0; i < textArr.length; i++) {
         console.log(
           'From first: ' + textArr[i],
           'From Last: ' + textArr[arrySize - 1 - i]
         )
         if (
           compareChar(textArr[i], textArr[arrySize - 1 - i]) === false
         ) {
           isPolindrome = false
           break
         }
       }
    }
  }

  if(isPolindrome){
   console.log("is polindrome")
  }else{
   console.log("Is not polindrome")
  }
}

isPolindrome('')