81 lines
3.2 KiB
Markdown
81 lines
3.2 KiB
Markdown
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---
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title: Freecodecamp Algorithm Bubble Sort Guide
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---
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Bubble sort is a simple sorting algorithm. This sorting algorithm is comparison based algorithm in which each pair of adjacent elements is
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compared and elements are swapped if they are not in order. This algorithm does sorting in-place i.e. it does not creates a new array while
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carrying out the sorting process.
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#### Example
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<a href='http://www.sorting-algorithms.com/bubble-sort' target='_blank' rel='nofollow'>Animation of BubbleSort</a>
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array = <a href='https://repl.it/CXif' target='_blank' rel='nofollow'>5, 1, 4, 2, 8]
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First Pass:
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( 5 1 4 2 8 ) –> ( 1 5 4 2 8 ), Here, algorithm compares the first two elements, and swaps since 5 > 1.
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( 1 5 4 2 8 ) –> ( 1 4 5 2 8 ), Swap since 5 > 4
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( 1 4 5 2 8 ) –> ( 1 4 2 5 8 ), Swap since 5 > 2
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( 1 4 2 5 8 ) –> ( 1 4 2 5 8 ), Now, since these elements are already in order (8 > 5), algorithm does not swap them.
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Second Pass:
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( 1 4 2 5 8 ) –> ( 1 4 2 5 8 )
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( 1 4 2 5 8 ) –> ( 1 2 4 5 8 ), Swap since 4 > 2
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( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
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( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
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Now, the array is already sorted, but our algorithm does not know if it is completed. The algorithm needs one whole pass without any
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swap to know it is sorted.
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Third Pass:
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( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
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( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
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( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
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( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
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#### C++ Implementation
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// Function to implement bubble sort
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void bubble_sort(int array[], int n)
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{
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// Here n is the number of elements in array
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int temp;
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for(int i = 0; i < n-1; i++)
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{
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// Last i elements are already in place
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for(int j = 0; j < n-i-1; j++)
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{
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if (array[j] > array[j+1])
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{
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// swap elements at index j and j+1
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temp = array[j];
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array[j] = array[j+1];
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array[j+1] = temp;
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}
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}
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}
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}
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:rocket: [Run Code</a> #### Python Implementation
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def bubble_sort(arr):
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exchanges = True # A check to see if the array is already sorted so that no further steps gets executed
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i = len(arr)-1
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while i > 0 and exchanges:
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exchanges = False
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for j in range(i):
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if arr<a href='https://forum.freecodecamp.com/images/emoji/emoji_one/rocket.png?v=3 ":rocket:"' target='_blank' rel='nofollow'>j]>arr[j+1]:
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exchanges = True
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arr[j], arr[j+1] = arr[j+1], arr[j]
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i -= 1
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arr = [5,3,23,1,43,2,54]
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bubble_sort(arr)
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print(arr) # Prints [1, 2, 3, 5, 23, 43, 54]
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 <a href='https://repl.it/CW0M/1' target='_blank' rel='nofollow'>Run Code</a>
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#### <a href='https://www.freecodecamp.com/videos/big-o-notation-what-it-is-and-why-you-should-care' target='_blank' rel='nofollow'>Complexity of Algorithm</a>
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**Worst and Average Case Time Complexity:** O(n*n). Worst case occurs when array is reverse sorted i.e. the elements are in decreasing order
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**Best Case Time Complexity:** O(n). Best case occurs when array is already sorted.
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