Bubble Sort

Bubble Sort is a comparison based sorting algorithm. In this algorithm adjacent elements are compared and swapped to make the correct sequence. This algorithm is simpler than other algorithms, but it has some drawbacks also. This algorithm is not suitable for a large number of data set. It takes much time to solve the sorting tasks.

The complexity of the Bubble Sort Technique

• Time Complexity: O(n) for best case, O(n^2) for average and worst case
• Space Complexity: O(1)

Input and Output

Input:
A list of unsorted data: 56 98 78 12 30 51
Output:
Array after Sorting: 12 30 51 56 78 98

Algorithm

bubbleSort( array, size)

Input − An array of data, and the total number in the array

Output − The sorted Array

Begin
   for i := 0 to size-1 do
      flag := 0;
      for j:= 0 to size –i – 1 do
         if array[j] > array[j+1] then
            swap array[j] with array[j+1]
            flag := 1
      done

      if flag ≠ 1 then
         break the loop.
   done
End

Example

#include<iostream>
using namespace std;

void swapping(int &a, int &b) { //swap the content of a and b
   int temp;
   temp = a;
   a = b;
   b = temp;
}

void display(int *array, int size) {
   for(int i = 0; i<size; i++)
      cout << array[i] << " ";
   cout << endl;
}

void bubbleSort(int *array, int size) {
   for(int i = 0; i<size; i++) {
      int swaps = 0; //flag to detect any swap is there or not
      for(int j = 0; j<size-i-1; j++) {
         if(array[j] > array[j+1]) { //when the current item is bigger than next
            swapping(array[j], array[j+1]);
            swaps = 1; //set swap flag
         }
      }
      if(!swaps)
         break; // No swap in this pass, so array is sorted
   }
}

int main() {
   int n;
   cout << "Enter the number of elements: ";
   cin >> n;
   int arr[n]; //create an array with given number of elements
   cout << "Enter elements:" << endl;

   for(int i = 0; i<n; i++) {
      cin >> arr[i];
   }

   cout << "Array before Sorting: ";
   display(arr, n);
   bubbleSort(arr, n);

   cout << "Array after Sorting: ";
   display(arr, n);
}

Output

Enter the number of elements: 6
Enter elements:
56 98 78 12 30 51
Array before Sorting: 56 98 78 12 30 51
Array after Sorting: 12 30 51 56 78 98