Saturday, 30 April 2016

Bubble Sort in C++

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Bubble Sort is the simplest sorting algorithm that works by repeatedly swapping the adjacent elements if they are in wrong order.

Example:
First Pass:
( 5 1 4 2 8 ) –> ( 1 5 4 2 8 ), Here, algorithm compares the first two elements, and swaps since 5 > 1.
( 1 5 4 2 8 ) –>  ( 1 4 5 2 8 ), Swap since 5 > 4
( 1 4 5 2 8 ) –>  ( 1 4 2 5 8 ), Swap since 5 > 2
( 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.

Second Pass:
( 1 4 2 5 8 ) –> ( 1 4 2 5 8 )
( 1 4 2 5 8 ) –> ( 1 2 4 5 8 ), Swap since 4 > 2
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –>  ( 1 2 4 5 8 )
Now, the array is already sorted, but our algorithm does not know if it is completed. The algorithm needs one whole pass without any swap to know it is sorted.

Third Pass:
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )

Following are implementations of Bubble Sort.

Code:
// C program for implementation of Bubble sort
#include<iostream>
using namespace std;

void swap(int *xp, int *yp)
{
       int temp = *xp;
       *xp = *yp;
       *yp = temp;
}

// A function to implement bubble sort
void bubbleSort(int arr[], int n)
{
       int i, j;
       for (i = 0; i < n - 1; i++)

              // Last i elements are already in place  
              for (j = 0; j < n - i - 1; j++)
                     if (arr[j] > arr[j + 1])
                           swap(&arr[j], &arr[j + 1]);
}

/* Function to print an array */
void printArray(int arr[], int size)
{
       for (int i = 0; i < size; i++)
              cout << arr[i] << endl;
}

// Driver program to test above functions
int main()
{
       int arr[] = { 64, 34, 25, 12, 22, 11, 90 };
       int n = sizeof(arr) / sizeof(arr[0]);
       bubbleSort(arr, n);
       cout<<"Sorted array: "<<endl;
       printArray(arr, n);
       return 0;

}



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