Swap Nodes in Pairs - Daily JS (Day 20)

Problem Statement
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's nodes (i.e., only nodes themselves may be changed.)

Examples
Example 1:

Input: head = [1,2,3,4]
Output: [2,1,4,3]

Example 2:

Input: head = []
Output: []

Example 3:

Input: head = [1]
Output: [1]

Constraints:

The number of nodes in the list is in the range [0, 100].
0 <= Node.val <= 100

Solution

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
const swapPairs = (n) => {
    if (n === null) {
        return null
    }
    if (n.next === null) {
        return n
    }
    let n1 = n.next
    let n2 = n.next.next
    n1.next = n
    n.next = swapPairs(n2)
    return n1
};

LeetCode issue:
https://leetcode.com/problems/swap-nodes-in-pairs/

How to implement a Linked List?

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