Bubble Sort program in C with Algorithm Explanation

In this Searching and Sorting in C Programs, we will have a look at implementations of Bubble Sort in C Programing Language. 

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

Example:

Take an array of numbers ” 5 1 4 2 8″, and sort the array from lowest number to greatest number using bubble sort. In each step, elements written in bold are being compared. Three passes will be required;

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 the 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 )

Bubble Sort program in C

#include <stdio.h>
int main()
{
  int array[100], n, c, d, swap;
  printf("Enter number of elements\n");
  scanf("%d", &n);
  printf("Enter %d integers\n", n);
  for (c = 0; c < n; c++)
    scanf("%d", &array[c]);
  for (c = 0 ; c < n - 1; c++)
   {
    for (d = 0 ; d < n - c - 1; d++)
    {
      if (array[d] > array[d+1]) /* For decreasing order use < */
      {
        swap       = array[d];
        array[d]   = array[d+1];
        array[d+1] = swap;
      }
    }
  }
  printf("Sorted list in ascending order:\n");
  for (c = 0; c < n; c++)
     printf("%d\n", array[c]);
  return 0;
}

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