algs4js/dist/sorting/QuickSort.js

Basic algorithms and data structures implemented with es6

'use strict';

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 QuickSort
 *
 * Implementation of the Quick Sort algorithm using the
 * Hoare partition algorithm.
 */
var QuickSort = function () {
  function QuickSort() {
    _classCallCheck(this, QuickSort);
  }

  _createClass(QuickSort, null, [{
    key: 'sort',
    value: function sort(arr) {
      this.quickSort(arr, 0, arr.length - 1);
    }
  }, {
    key: 'quickSort',
    value: function quickSort(arr, left, right) {
      var idx = this.partition(arr, left, right);
      if (right <= left) {
        return;
      }
      this.quickSort(arr, left, idx);
      this.quickSort(arr, idx + 1, right);
    }

    /* eslint no-param-reassign: 0 */

  }, {
    key: 'partition',
    value: function partition(arr, first, last) {
      // Protect against overflow by adding delta to first index
      var pivot = arr[Math.floor(first + (last - first) / 2)];
      // Hoare algorithm: start outside bounds for cleaner loop code
      var left = first - 1;
      var right = last + 1;
      while (left < right) {
        while (arr[++left] < pivot) {}
        while (arr[--right] > pivot) {}
        if (left < right) {
          this.swap(arr, left, right);
        }
      }
      _LogUtil2.default.debug('Before return: left => ' + left + ', right => ' + right);
      return right;
    }
  }, {
    key: 'swap',
    value: function swap(arr, i, j) {
      var tmp = arr[i];
      arr[i] = arr[j];
      arr[j] = tmp;
    }
  }]);

  return QuickSort;
}();

module.exports = QuickSort;