mathball/lib/ugly/index.js

A JavaScript library for Competitive Programming

'use strict';

/**
 * Find nth Ugly Number
 */
var validate = require('../validation/positive-integer');

var maxDivide = function maxDivide(num, a) {
  while (num % a === 0) {
    num /= a;
  }

  return num;
};

var isUgly = function isUgly(num) {
  num = maxDivide(num, 2);
  num = maxDivide(num, 3);
  num = maxDivide(num, 5);

  return num === 1;
};

var getNthUglyNumber = function getNthUglyNumber(n) {
  var count = 1;
  var i = 1;

  while (n > count) {
    i += 1;

    if (isUgly(i)) {
      count += 1;
    }
  }

  return i;
};

exports.find = function (n) {
  validate(n, 'ugly');

  return getNthUglyNumber(n);
};