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50 lines
1.1 KiB
JavaScript
50 lines
1.1 KiB
JavaScript
(function (exports) {
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'use strict';
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/**
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* Advanced (optimised) method for checking if provided number is prime.
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* For example for number 104743 it should return true, for 104744 - false.
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*
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* @module primes/is-prime
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* @param {Number} number - Number that we check on prime.
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* @returns {Boolean} Will return true if provided number is prime.
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*
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* @example
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* var isPrime = require('path-to-algorithms/src/is-prime').isPrime;
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*
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* console.log(isPrime(7)); // true
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* console.log(isPrime(18)); // false
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*/
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exports.isPrime = function (number) {
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if (number < 2) {
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return false;
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}
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if (number % 2 === 0) {
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return (number === 2);
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}
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if (number % 3 === 0) {
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return (number === 3);
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}
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var horizon = Math.floor(Math.sqrt(number));
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var factor = 5;
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while (factor <= horizon) {
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if (number % factor === 0) {
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return false;
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}
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if (number % (factor + 2) === 0) {
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return false;
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}
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factor += 6;
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}
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return true;
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};
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}(typeof exports === 'undefined' ? window : exports));
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