merge: Bubble Sort enhancements for nearly sorted or sorted array, added test cases and documentation (TheAlgorithms#895)

* BubbleSort enacements for nearly sorted or sorted array and added test cases * BubbleSort enacements for nearly sorted or sorted array and added test cases * Bubble sort requested changes solved * standard js style issue fixed

Author: aminhossain

Sorts/BubbleSort.js

@@ -2,6 +2,7 @@
 * compares adjacent element and swaps their position
 * The big O on bubble sort in worst and best case is O(N^2).
 * Not efficient.
+* Somehow if the array is sorted or nearly sorted then we can optimize bubble sort by adding a flag.
 *
 * In bubble sort, we keep iterating while something was swapped in
 * the previous inner-loop iteration. By swapped I mean, in the
@@ -17,16 +18,23 @@
  */
 export function bubbleSort (items) {
  const length = items.length
+ let noSwaps
 
- for (let i = (length - 1); i > 0; i--) {
+ for (let i = length; i > 0; i--) {
+ // flag for optimization
+ noSwaps = true
  // Number of passes
- for (let j = (length - i); j > 0; j--) {
+ for (let j = 0; j < (i - 1); j++) {
  // Compare the adjacent positions
- if (items[j] < items[j - 1]) {
+ if (items[j] > items[j + 1]) {
  // Swap the numbers
- [items[j], items[j - 1]] = [items[j - 1], items[j]]
+ [items[j], items[j + 1]] = [items[j + 1], items[j]]
+ noSwaps = false
  }
  }
+ if (noSwaps) {
+ break
+ }
  }
 
  return items

Sorts/test/BubbleSort.test.js

@@ -6,6 +6,7 @@ describe('bubbleSort', () => {
  expect(bubbleSort([])).toEqual([])
  expect(bubbleSort([1, 2, 3])).toEqual([1, 2, 3])
  expect(bubbleSort([5, 6, 7, 8, 1, 2, 12, 14])).toEqual([1, 2, 5, 6, 7, 8, 12, 14])
+ expect(bubbleSort([5, 6, 7, 8, 9, 4])).toEqual([4, 5, 6, 7, 8, 9])
  })
 })