algs4js/dist/dynamic-programming/Factorial.js

Basic algorithms and data structures implemented with es6

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

var _LogUtil = require('../util/LogUtil');

var _LogUtil2 = _interopRequireDefault(_LogUtil);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

/**
 * Class Factorial
 *
 * Exposes static fucntionality for generating the factorial of a number.
 */
var Factorial = function () {
  function Factorial() {
    _classCallCheck(this, Factorial);
  }

  _createClass(Factorial, null, [{
    key: 'validate',


    /**
     * Validates if the passed in number is an integer of zero or greater
     *
     * @param {number} num, the number to validate
     * @throws {Error} error, if not an  integer >= 0
     */
    value: function validate(num) {
      var isValid = Number.isInteger(num) && num >= 0;
      _LogUtil2.default.debug('isValid for ' + num + ': ' + isValid);
      if (!isValid) {
        throw new Error(num + ' is not a valid integer >= 0');
      }
    }

    /**
     * Uses dynamic programming to calculate the factorial of a number, n!.
     *
     * Algorithm:
     * X(i) = Sequence {1, 2, 3, ..., i}
     * F(i) = Factorial for X(i)
     * F(1) = 1;
     * F(i) = F(i-1) * X(i)
     *
     * @param {number} num, the number to calculate its factorial
     * @returns {number} the factorial
     */

  }, {
    key: 'calc',
    value: function calc(num) {
      this.validate(num);
      _LogUtil2.default.debug('Calculating the factorial of ' + num);
      var fim1 = 1;
      var fi = fim1;
      for (var i = 2; i <= num; i++) {
        fi = fim1 * i;
        fim1 = fi;
      }
      return fi;
    }
  }]);

  return Factorial;
}();

exports.default = Factorial;