Sort the array based on position without extra space

Question:

Write a program to sort the array based on position. Sort odd position elements in descending order and even position elements in ascending order. Must not use any extra array.

Logic

• The logic is very simple, sort the odd position elements separately and even position elements separately.
• Use insertion sorting method to sort the odd position numbers.
• After that sort the even position numbers.
• Finally, print the array.

Program

#include<stdio.h>
void swap(int* ,int*);
void main()
{
	 int ar[20];
	 int n,i,k,j,m,temp; 
	 printf("enter limit");
	 scanf("%d",&n);

	for( i =0;i<n;i++)
	{
		scanf("%d",&ar[i]);
	}
											// insertion sort for odd position
	for(i=0;i<=n-3; i=temp+2)
	{ 
		temp=i;								// store the index so not affected in next iteration
		while(i>=0)
		{
			if(ar[i]<ar[i+2])				// if ar[i] is small
			{
				swap(&ar[i],&ar[i+2]);
				i=i-2;						//decrement to check previous odd position,ar[i] and ar[i-2] in next iteration
			}
			else
				break;						// end loop when sorting finised

		}
	}
										
	for(j=1;j<=n-3;j=temp+2)				// insertion sort for even position
	{ 
		temp=j;
		while(j>=1)
		{
			if(ar[j]>ar[j+2])				//if ar[i] is large
			{ 	swap(&ar[j],&ar[j+2]);
				j=j-2;
			}
			else
				break;

		}
	}

	for( k=0;k<n;k++)
		printf("%d ",ar[k]);				//sorted array
	
}
							
void swap(int *a,int *b)					//call by reference swap
{ 
	int temp ; 
	temp = *a;
	*a = *b;
	*b = temp;
}