Timer is Running

Given a singly linked list of size N. The task is to swap elements in the linked list pairwise.
For example, if the input list is 1 2 3 4, the resulting list after swaps will be 2 1 4 3.

The first line of input contains the number of test cases T. For each test case, the first line of input contains the length of the linked list and the next line contains linked list data.

Output the linked list after swapping pairwise nodes.

User Task:
The task is to complete the function pairWiseSwap() which takes the head node as the only argument and returns the modified head.

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

1 <= T <= 100
1 <= N <= 103

1 2 2 4 5 6 7 8

2 1 4 2 6 5 8 7

Testcase 1:
After swapping each pair considering (1,2), (2, 4), (5, 6).. so on as pairs, we get 2, 1, 4, 2, 6, 5, 8, 7 as a new linked list.


** For More Input/Output Examples Use 'Expected Output' option **

Contributor: Harshit Sidhwa
Author: Karan Grover

If you have purchased any course from GeeksforGeeks then please ask your doubt on course discussion forum. You will get quick replies from GFG Moderators there.

Need help with your code? Please use ide.geeksforgeeks.org, generate link and share the link here.

to report an issue on this page.