Swap Nodes in Pairs
MediumP2Coding
Given the head of a singly linked list, swap every two adjacent nodes and return the head of the new list. If the length is odd, the last node stays where it is. Change the pointers; do not just swap the values. A list node has val and next. The ListNode class is already defined for you.
Example 1
- Input
- head = [1,2,3,4]
- Output
- [2,1,4,3]
Example 2
- Input
- head = [1,2,3]
- Output
- [2,1,3]
Example 3
- Input
- head = []
- Output
- []
Constraints
- 0 <= number of nodes <= 100
- 0 <= Node.val <= 100
Hints
Give it a real attempt first. Run shows which examples fail.
Saved automatically
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