mathball/lib/prime/index.js

A JavaScript library for Competitive Programming

'use strict';

/* Prime Number
 * Function: isPrime()
 */

var validate = require('../validation/positive-integer');

exports.check = function (num) {
  validate(num, 'isPrime');
  if (num === 2 || num === 3) {
    return true;
  }
  if (num < 2 || num % 2 === 0) {
    return false;
  }
  if (num < 9) {
    return true;
  }
  if (num % 3 === 0) {
    return false;
  }
  var r = Math.sqrt(num);
  var f = 5;
  while (f <= r) {
    if (num % f === 0) {
      return false;
    }
    if (num % (f + 2) === 0) {
      return false;
    }
    f = f + 6;
  }
  return true;
};

/* Range of Prime Numbers
 * Function: rangePrime()
 */

exports.range = function (n) {
  validate(n, 'rangePrime');
  var numbers = Array(n + 1).fill(true);
  numbers[0] = numbers[1] = false;
  var primeNumbers = [];
  for (var i = 0; i < numbers.length; i++) {
    if (numbers[i]) {
      primeNumbers.push(i);
      for (var j = i; j <= n; j += i) {
        numbers[j] = false;
      }
    }
  }
  return primeNumbers;
};