Shuffle the position of each Array element by swapping adjacent elements

Given an array arr[], the task is to rearrange the array elements by swapping adjacent elements such that no element remains at the same position after swapping.
 

Examples:

Input: arr[] = { 1, 2, 3, 4, 5 } 
Output: 2 1 5 3 4 
Explanation: 
Adjacent elements are swapped as follows: 
(1, 2 -> 2, 1) 
(3, 4, 5 -> 5, 3, 4)
Input: arr[] = {1, 2, 3, 4} 
Output: 2 1 4 3 
Explanation: 
Adjacent elements are swapped as follows: 
1, 2 -> 2, 1 
3, 4 -> 4, 3

Approach: The key observation in the problem is that there can be two cases for the arrays to swap the array elements:
 

• If the length of the array is even then we can easily Swap 2 Variables without using 3rd variable for every pair of contiguous elements.
• If the length of the array is odd then we can do the same as above, but the last 3 elements will not form a pair, So will we can easily Swap those 3 Variables without using 4th variable.

Below is the implementation of the above approach:
 

2 1 4 5 3

Time Complexity: O(N) 
Auxiliary Space: O(1)