Add BubbleSort.

Author: trekhleb

src/algorithms/sorting/SortTester.js

@@ -1,6 +1,7 @@
-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 const sortedArr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20];
+export const reverseArr = [20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1];
+export const notSortedArr = [15, 8, 5, 12, 10, 1, 16, 9, 11, 7, 20, 3, 2, 6, 17, 18, 4, 13, 14, 19];
+export const equalArr = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1];
 
 export class SortTester {
   static testSort(SortingClass) {
@@ -11,9 +12,10 @@ export class SortTester {
     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]);
+    expect(sorter.sort(sortedArr)).toEqual(sortedArr);
+    expect(sorter.sort(reverseArr)).toEqual(sortedArr);
+    expect(sorter.sort(notSortedArr)).toEqual(sortedArr);
+    expect(sorter.sort(equalArr)).toEqual(equalArr);
   }
 
   static testSortWithCustomComparator(SortingClass) {

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

@@ -2,9 +2,13 @@ import Sort from '../Sort';
 
 export default class BubbleSort extends Sort {
   sort(initialArray) {
+    // Flag that holds info about whether the swap has occur or not.
+    let swapped = false;
     const array = initialArray;
 
     for (let i = 0; i < array.length; i += 1) {
+      swapped = false;
+
       for (let j = 0; j < array.length - 1; j += 1) {
         // Call visiting callback.
         this.callbacks.visitingCallback(array[j]);
@@ -14,8 +18,17 @@ export default class BubbleSort extends Sort {
           const tmp = array[j + 1];
           array[j + 1] = array[j];
           array[j] = tmp;
+
+          // Register the swap.
+          swapped = true;
         }
       }
+
+      // If there were no swaps then array is already sorted and there is
+      // no need to proceed.
+      if (!swapped) {
+        return array;
+      }
     }
 
     return array;

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

@@ -0,0 +1,66 @@
+import BubbleSort from '../BubbleSort';
+import {
+  equalArr,
+  notSortedArr,
+  reverseArr,
+  sortedArr,
+  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);
+
+    const arrayAfterSorting = sorter.sort(sortedArr);
+
+    expect(arrayAfterSorting).toEqual(sortedArr);
+    expect(visitingCallback).toHaveBeenCalledTimes(19);
+  });
+
+  it('should visit not-sorted array element specified number of times', () => {
+    const visitingCallback = jest.fn();
+
+    const callbacks = { visitingCallback };
+    const sorter = new BubbleSort(callbacks);
+
+    const arrayAfterSorting = sorter.sort(notSortedArr);
+
+    expect(arrayAfterSorting).toEqual(sortedArr);
+    expect(visitingCallback).toHaveBeenCalledTimes(19);
+  });
+
+  it('should visit equal array element specified number of times', () => {
+    const visitingCallback = jest.fn();
+
+    const callbacks = { visitingCallback };
+    const sorter = new BubbleSort(callbacks);
+
+    const arrayAfterSorting = sorter.sort(equalArr);
+
+    expect(arrayAfterSorting).toEqual(equalArr);
+    expect(visitingCallback).toHaveBeenCalledTimes(19);
+  });
+
+  it('should visit reverse sorted array element specified number of times', () => {
+    const visitingCallback = jest.fn();
+
+    const callbacks = { visitingCallback };
+    const sorter = new BubbleSort(callbacks);
+
+    const arrayAfterSorting = sorter.sort(reverseArr);
+
+    expect(arrayAfterSorting).toEqual(sortedArr);
+    expect(visitingCallback).toHaveBeenCalledTimes(19);
+  });
+});