#18 - Previous multiple of three CodeWars Kata (7 kyu)

Instructions

Given a positive integer n: 0 < n < 1e6, remove the last digit until you're left with a number that is a multiple of three.

Return n if the input is already a multiple of three, and return null if no such number exists.

Examples

1 => null
25 => null
36 => 36
1244 => 12
952406 => 9

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My solution:

const prevMultOfThree = n => {
  let arr = n.toString().split('')

  for(let i = 0; i<arr.length; i++){
    for(let j = 0; j<arr.length; i++){
      let sum = +arr.join('')
      if( sum % 3 === 0) return sum 
      arr.pop()
    }

    return null
  }

}

Explanation

First I splitted the number into an string array

let arr = n.toString().split('')

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Then after that I used a loop that iterated until i is equal to the array length.
Inside of this array I used anothe for loop that still iterated the same array, inside of this loop I made the variable "sum" that is equal to the array joined and converted it to a number with the + operator, after that I added a conditional that checked if it is divisible by 3, if it is divisible by 3 it will return 3, but if not it will continue the loop but with the array without the last element, using arr.pop()

for(let j = 0; j<arr.length; i++){
let sum = +arr.join('')
if( sum % 3 === 0) return sum
arr.pop()
}

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if the loop is over and the array is still empty, it means that any number was divisible by 3, so it returns null

return null

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