one_var_bubble_sort.c

//************************************************************************//
//	one_var_bubble_sort.c                                                 //
//************************************************************************//
//									 
//	AUTHOR: 		Patrick Michaelsen
//	EMAIL: 			PatrickMichaelsen@PatrickMichaelsen.com 
//				MichaelsenPatrick@gmail.com
//	WEBSITE:		PatrickMichaelsen.com
//	
//	DESCRIPTION:		This algorithm bubble sorts an array of 
//				integers with the use of only one local 
//				variable in O(n²) time
//
//************************************************************************//

#include <stdio.h>
#include <stdlib.h> 

int main()
{

	//************************************************************************//
	//	END INITIALIZATION												      //
	//************************************************************************//
	//	This code is considered preparatory and is not
	//	part of the algorithm. 
	//************************************************************************//

	 int arr[10] = {5,9,1,4,7,8,6,3,2,0};
	
		for( int k = 0; k < sizeof(arr)/sizeof(int); k++ )
			printf(" %d ",arr[k]);
		printf("\n");

	//************************************************************************//
	//	END INITIALIZATION													  //
	//************************************************************************//
 
		//********************// 
		//  BEGIN ALGORITHM   //
		//********************//
  
		//i is the index and flag
		int i = 1;

		//loop while no swaps 
		//made in last iteration
		while ( i )
		{ 
		//loop through list
		//to compare every pair 
			while ( abs(i) < (sizeof(arr)/sizeof(int)) )
		{	
			//if pair is out of order 
			if ( arr[abs(i)-1] > arr[abs(i)] )
					{
				//swap
						arr[abs(i)-1] = arr[abs(i)] ^ arr[abs(i)-1];
						arr[abs(i)]   = arr[abs(i)] ^ arr[abs(i)-1];
						arr[abs(i)-1] = arr[abs(i)] ^ arr[abs(i)-1];
				
				//set swap flag
				i = -abs(i);
			}
		
			//increment i	
			i += abs(i+1) - abs(i);
		}

		if( i == sizeof(arr)/sizeof(int) )
			i = 0;
		else if ( -i == sizeof(arr)/sizeof(int) )
			i = 1;
	}

	//********************// 
	//  END ALGORITHM     //
	//********************//

 
	printf("\n");
	for( int k = 0; k < sizeof(arr)/sizeof(int); k++ )
		printf(" %d ",arr[k]);
	printf("\n");

	return 0;
}