Bubble sort algorithm using Javascript

Sorting is a very useful technique in many algorithms and programs. Basically, sorting operations help us to arrange a set of data in a particular manner. Bubble sort is one of the basic and easiest sorting approaches. Let's take an example to discuss sorting.

Before sorting:

30

40

20

10

60

70

80

50

100

90

After sorting:

10

20

30

40

50

60

70

80

90

100

We have numbers in an array, and we want to arrange them in increasing order. To solve this problem, we have to use sorting.

Input-

[30, 40, 20, 10, 60, 70, 80, 50, 100, 90]

Output-

[10, 20, 30, 40, 50, 60, 70, 80, 90, 100]

Explanation- We have sorted the given array in increasing order.

Bubble Sort : - Bubble sort is an easy and slow sorting algorithm. This sorting algorithm is a comparison-based algorithm in which each pair of adjacent elements is compared. After that they are swapped if they are not in order.

Algorithm:-

Step 1: Start

Step 2: All values are taken from the user to build an array.

Step 3: Array is created.

Step 4: A function is called. This function takes the array as input and processes it.

Step 5: We traverse the array n times (n is the size of the array).

Step 6: If we find any element is bigger than its next element, then we swap them.

Step 7: After repeating step 6 in every traversal, we get the sorted array.

Step 8: The returned array will be printed.

Step 9: Stop.

Pseudocode:

Begin bubblesort( list )
			for all elements of list
				if list[ I ] > list[ i+1 ] 
					swap( list[ I ], list[ i+1 ]  )
				end if
			end for
		end bubblesort

Explanation of Algorithm: -

14

33

27

35

10

Let's try to understand the algorithm with this unsorted array. So, the process of sorting starts with the very first two elements. We compare them to check which one is greater.

14

33

27

35

10

In this case, 33 is greater than 14, so it is sorted already. Now we go to the next step.

14

33

27

35

10

14

27

33

35

10

In this case, 33 is greater than 27, so we swap them. In this way, we traverse all the elements of the array. After the first traversal, we get the last element sorted, and after n times traversal, all elements will be sorted.

Step 1:

14

27

33

10

35

Step 2:

14

27

10

33

35

Step 3:

14

10

27

33

35

Step 4:

10

14

27

33

35

Code: -

function bubbleSort( arr ){


var i, j;
var len = arr.length;


var isSwapped = false;


for(i =0; i < len; i++){
	
	isSwapped = false;
	
	for(j = 0; j < len; j++){
		if(arr[j] > arr[j + 1]){
		var temp = arr[j]
		arr[j] = arr[j+1];
		arr[j+1] = temp;
		isSwapped = true;
		}
	}
	
	// IF no two elements were swapped by the inner loop, then break
	
	if(!isSwapped){
	break;
	}
}


// Print the array
console.log(arr)
}


// calling the bubbleSort Function
bubbleSort(arr)

Complexity Analysis: -

Time complexity- Bubble sort compares the adjacent elements, hence the number of comparisons

                        = ( n – 1 ) + ( n – 2 ) + ( n – 3 ) + ( n – 4 ) + ( n – 5 ) + ( n – 6 ) + ( n – 7 ) + ……… + 1

                        = n ( n - 1 ) / 2

                        = n^2

Time complexity = O ( n^2 )

Worst case: If we want to sort in ascending order and the array is in descending order, then the worst case occurs. Here time complexity will be O( n^2 ).

Best case: If the array is sorted already.

Space complexity- In this solution, we use constant memory. So, space complexity will be O(1).

Uses of bubble sort: It is a very simple algorithm, so it is often used by beginner-level programmers. It is very helpful to understand the basic concept of sorting. In the polygon filling algorithm, it is used. But as its time complexity is very high so in many algorithms, bubble sort is avoided. Instead of bubble sort, in many cases, merge sort or quick sort is used.