aloalgoSwap Nodes in Pairs
Medium
You are given a linked list.
Your task is to swap every two adjacent nodes in the linked list and return the head of the modified list.
Note that:
- Only the node pointers should be modified; the
valueof the nodes must remain unchanged.
Return the head of the modified linked list.
Example 1
Input
1 → 2 → 3 → 4 → null
Output
2 → 1 → 4 → 3 → null
Explanation:
The first pair (1, 2) is swapped to (2, 1). The second pair (3, 4) is swapped to (4, 3).
Example 2
Input
None
Output
None
Explanation:
An empty list remains empty.
Example 3
Input
1 → null
Output
1 → null
Explanation:
A list with a single node remains unchanged.
Example 4
Input
1 → 2 → 3 → null
Output
2 → 1 → 3 → null
Explanation:
The pair (1, 2) is swapped to (2, 1). The last node (3) is left as is.
Input
1 → 2 → 3 → 4 → null
Output
2 → 1 → 4 → 3 → null