Swap Nodes in Pairs
Explore how to swap every two adjacent nodes in a singly linked list by manipulating the nodes themselves without altering their values. This lesson helps you implement an efficient in-place solution that runs in linear time and constant space, enhancing your skills in linked list manipulation and coding interview problem solving.
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Statement
Given a singly linked list, swap every two adjacent nodes of the linked list. After the swap, return the head of the linked list.
Note: Solve the problem without modifying the values in the list’s nodes. In other words, only the nodes themselves can be changed.
Constraints:
- The number of nodes in the list is in the range .
-
Node.value
Examples
Understand the problem
Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:
Swap Nodes in Pairs
Which updated linked list do we get as a result of swapping the nodes in pairs for the linked list given below?
1 → 2 → 3 → 4 → 5 → 6
1 → 2 → 3 → 4 →5 → 6
1 → 3 → 2 → 4 → 5 → 6
2 → 1 → 4 → 3 → 6 → 5
6 → 5 → 4 → 3 → 2 → 1
Figure it out!
We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.
Note: As an additional challenge, we have intentionally hidden the solution to this puzzle.
Try it yourself
Implement your solution in the following coding playground.
We have left the solution to this challenge as an exercise for you. The optimal solution to this problem runs in O(n) time and takes O(1) space. You may try to translate the logic of the solved puzzle into a coded solution.
# Definition for a Linked List node# class ListNode:# def __init__(self, val=0, next=None):# self.val = val# self.next = nextfrom ds_v1.LinkedList.LinkedList import ListNodedef swap_pairs(head):# Replace this placeholder return statement with your codereturn head