Add a comparator and improve code style

mik-laj · mik-laj · commit 704669a2ae0d · 2017-06-07T19:11:22.000+02:00
diff --git a/src/sorting/quicksort-functional.js b/src/sorting/quicksort-functional.js
@@ -2,35 +2,66 @@
 
   'use strict';
 
+  function compare(a, b) {
+    return a - b;
+  }
+
   /**
-   * The quicksort algorithm (functional variant). It's complexity is O(nlog n).
+   * Quicksort algorithm (functional variant)
    *
    * @public
+   * @param {array} array Array which should be sorted.
+   * @return {array} Sorted array.
    */
   var quickSort = (function () {
 
     /**
-     * Sorts given array.
+     * Recursively calls itself.
      *
      * @private
-     * @param {array} array Array which should be sorted
-     * @returns {array} array Sorted array
+     * @param {array} array Array which should be processed
      */
-    return function quickSort(array, left, right, cmp) {
-      if ( arr.length < 1) {
+    return function quickSort(array, cmp) {
+      if (arr.length < 1) {
         return arr;
       }
 
-      var [x, ...rest] = arr;
+      const [x, ...rest] = arr;
 
       return [
-          ...quickSort(rest.filter(v => v <= x)),
+          ...quickSort(rest.filter(v => cmp(v, x) < 0),
           x,
-          ...quickSort(rest.filter(v => v  > x))
+          ...quickSort(rest.filter(v => cmp(v, x) >= 0))
       ]
       return array;
     }
 
+
+    /**
+     * Quicksort algorithm. In this version of quicksort used
+     * functional programming mechanisms.<br><br>
+     * Time complexity: O(N log(N)).
+     *
+     * @example
+     *
+     * var sort = require('path-to-algorithms/src' +
+     * '/sorting/quicksort-functional').quickSort;
+     * console.log(sort([2, 5, 1, 0, 4])); // [ 0, 1, 2, 4, 5 ]
+     *
+     * @public
+     * @module sorting/quicksort-functional
+     * @param {Array} array Input array.
+     * @param {Function} cmp Optional. A function that defines an
+     * alternative sort order. The function should return a negative,
+     * zero, or positive value, depending on the arguments.
+     * @return {Array} Sorted array.
+     */
+    return function (array, cmp) {
+      cmp = cmp || compare;
+      quicksort(array, 0, array.length - 1, cmp);
+      return array;
+    };
+
   }());
 
   exports.quickSort = quickSort;
diff --git a/test/sorting/quicksort-functional.spec.js b/test/sorting/quicksort-functional.spec.js
@@ -2,4 +2,4 @@ var sortTestCase = require('./sort.testcase.js');
 var quickSort =
       require('../../src/sorting/quicksort-functional.js').quickSort;
 
-sortTestCase(quickSort, 'Quick sort', { reverse: false });
+sortTestCase(quickSort, 'Quick sort');
