7-9-21.js

// Palindrome chain length

// Number is a palindrome if it is equal to the number with digits in reversed order. For example, 5, 44, 171, 4884 are palindromes, and 43, 194, 4773 are not.

// Write a function which takes a positive integer and returns the number of special steps needed to obtain a palindrome. The special step is: "reverse the digits, and add to the original number". If the resulting number is not a palindrome, repeat the procedure with the sum until the resulting number is a palindrome.

// If the input number is already a palindrome, the number of steps is 0.

// All inputs are guaranteed to have a final palindrome which does not overflow MAX_SAFE_INTEGER.

// Example
// For example, start with 87:

//   87 +   78 =  165     - step 1, not a palindrome
//  165 +  561 =  726     - step 2, not a palindrome
//  726 +  627 = 1353     - step 3, not a palindrome
// 1353 + 3531 = 4884     - step 4, palindrome!
// 4884 is a palindrome and we needed 4 steps to obtain it, so answer for 87 is 4.

// Additional info
// Some interesting information on the problem can be found in this Wikipedia article on Lychrel numbers.

var palindromeChainLength = function(n) {
    let stepCount = 0
    const checkPalindrome = num => num === Number(num.toString().split('').reverse().join(''))
    if (checkPalindrome(n)) return stepCount
    else {
      while (!checkPalindrome(n)){
          stepCount++
          n += Number(n.toString().split('').reverse().join(''))
      }
    }
    return stepCount
  };
  
  /*
  declare a reverseN variable that is assigned n backwards
  write a function to check if a number added to its reverseN will equal
      a palindrome
      the function should reverse the input number add it to the original
      and then check for palindrome
  run a while loop with a counter that will count the number of times 
      the function is run and also updates n to be the new sum
  */