Add BubbleSort.

Author: trekhleb

README.md

@@ -30,6 +30,8 @@
 * Graph
   * [Depth-First Search (DFS)](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/graph/depth-first-search)
   * [Breadth-First Search (BFS)](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/graph/breadth-first-search)
+* Sorting
+  * [Bubble Sort](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/sorting/bubble-sort)
 
 ## Running Tests
 

src/algorithms/sorting/Sort.js

@@ -0,0 +1,34 @@
+import Comparator from '../../utils/comparator/Comparator';
+
+/**
+ * @typedef {Object} SorterCallbacks
+ * @property {function(a: *, b: *)} compareCallback - If provided then all elements comparisons
+ *  will be done through this callback.
+ * @property {function(a: *)} visitingCallback - If provided it will be called each time the sorting
+ *  function is visiting the next element.
+ */
+
+export default class Sort {
+  constructor(rawCallbacks) {
+    this.callbacks = Sort.initSortingCallbacks(rawCallbacks);
+    this.comparator = new Comparator(this.callbacks.compareCallback);
+  }
+
+  /**
+   * @param {SorterCallbacks} rawCallbacks
+   * @returns {SorterCallbacks}
+   */
+  static initSortingCallbacks(rawCallbacks) {
+    const callbacks = rawCallbacks || {};
+    const stubCallback = () => {};
+
+    callbacks.compareCallback = callbacks.compareCallback || undefined;
+    callbacks.visitingCallback = callbacks.visitingCallback || stubCallback;
+
+    return callbacks;
+  }
+
+  sort() {
+    throw new Error('sort method must be implemented');
+  }
+}

src/algorithms/sorting/SortTester.js

@@ -0,0 +1,37 @@
+export const sortedArray = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+export const notSortedArray = [10, 5, 30, -1, 0, 0, 1, 2, -3, 2];
+export const equalArray = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1];
+
+export class SortTester {
+  static testSort(SortingClass) {
+    const sorter = new SortingClass();
+
+    expect(sorter.sort([])).toEqual([]);
+    expect(sorter.sort([1])).toEqual([1]);
+    expect(sorter.sort([1, 2])).toEqual([1, 2]);
+    expect(sorter.sort([2, 1])).toEqual([1, 2]);
+    expect(sorter.sort([1, 1, 1])).toEqual([1, 1, 1]);
+    expect(sorter.sort(sortedArray)).toEqual([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+    expect(sorter.sort(notSortedArray)).toEqual([-3, -1, 0, 0, 1, 2, 2, 5, 10, 30]);
+    expect(sorter.sort(equalArray)).toEqual([1, 1, 1, 1, 1, 1, 1, 1, 1, 1]);
+  }
+
+  static testSortWithCustomComparator(SortingClass) {
+    const callbacks = {
+      compareCallback: (a, b) => {
+        if (a.length === b.length) {
+          return 0;
+        }
+
+        return a.length < b.length ? -1 : 1;
+      },
+    };
+
+    const sorter = new SortingClass(callbacks);
+
+    expect(sorter.sort([''])).toEqual(['']);
+    expect(sorter.sort(['a'])).toEqual(['a']);
+    expect(sorter.sort(['aa', 'a'])).toEqual(['a', 'aa']);
+    expect(sorter.sort(['bb', 'aa', 'c'])).toEqual(['c', 'bb', 'aa']);
+  }
+}

src/algorithms/sorting/__test__/Sort.test.js

@@ -0,0 +1,12 @@
+import Sort from '../Sort';
+
+describe('Sort', () => {
+  it('should throw an error when trying to call Sort.sort() method directly', () => {
+    function doForbiddenSort() {
+      const sorter = new Sort();
+      sorter.sort();
+    }
+
+    expect(doForbiddenSort).toThrow();
+  });
+});

src/algorithms/sorting/bubble-sort/BubbleSort.js

@@ -0,0 +1,23 @@
+import Sort from '../Sort';
+
+export default class BubbleSort extends Sort {
+  sort(initialArray) {
+    const array = initialArray;
+
+    for (let i = 0; i < array.length; i += 1) {
+      for (let j = 0; j < array.length - 1; j += 1) {
+        // Call visiting callback.
+        this.callbacks.visitingCallback(array[j]);
+
+        // Swap elements if they are in wrong order.
+        if (this.comparator.lessThen(array[j + 1], array[j])) {
+          const tmp = array[j + 1];
+          array[j + 1] = array[j];
+          array[j] = tmp;
+        }
+      }
+    }
+
+    return array;
+  }
+}

src/algorithms/sorting/bubble-sort/README.md

@@ -0,0 +1,8 @@
+# Bubble Sort
+
+Bubble sort, sometimes referred to as sinking sort, is a 
+simple sorting algorithm that repeatedly steps through 
+the list to be sorted, compares each pair of adjacent 
+items and swaps them if they are in the wrong order. 
+The pass through the list is repeated until no swaps 
+are needed, which indicates that the list is sorted.

src/algorithms/sorting/bubble-sort/__test__/bubbleSort.test.js

@@ -0,0 +1,45 @@
+import BubbleSort from '../BubbleSort';
+import { equalArray, notSortedArray, sortedArray, SortTester } from '../../SortTester';
+
+describe('bubbleSort', () => {
+  it('should sort array', () => {
+    SortTester.testSort(BubbleSort);
+  });
+
+  it('should sort array with custom comparator', () => {
+    SortTester.testSortWithCustomComparator(BubbleSort);
+  });
+
+  it('should visit sorted array element specified number of times', () => {
+    const visitingCallback = jest.fn();
+
+    const callbacks = { visitingCallback };
+    const sorter = new BubbleSort(callbacks);
+
+    sorter.sort(sortedArray);
+
+    expect(visitingCallback).toHaveBeenCalledTimes(90);
+  });
+
+  it('should visit not-sorted array element specified number of times', () => {
+    const visitingCallback = jest.fn();
+
+    const callbacks = { visitingCallback };
+    const sorter = new BubbleSort(callbacks);
+
+    sorter.sort(notSortedArray);
+
+    expect(visitingCallback).toHaveBeenCalledTimes(90);
+  });
+
+  it('should visit equal array element specified number of times', () => {
+    const visitingCallback = jest.fn();
+
+    const callbacks = { visitingCallback };
+    const sorter = new BubbleSort(callbacks);
+
+    sorter.sort(equalArray);
+
+    expect(visitingCallback).toHaveBeenCalledTimes(90);
+  });
+});