Description
Given a linked list, swap every two adjacent nodes and return its head. You must solve the problem without modifying the values in the list nodes.
Examples
Input:
head = [1,2,3,4]Output:
[2,1,4,3]Explanation:
Swap pairs: (1,2) and (3,4).
Input:
head = []Output:
[]Explanation:
Edge case with empty result.
Input:
head = [5,8,1]Output:
[8,5,1]Explanation:
With an odd number of nodes, swap the first pair (5,8) to get (8,5), and leave the last node 1 unchanged since it has no pair.
Constraints
- •
0 ≤ list length ≤ 100