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Swap Nodes in Pairs

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.)

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

My 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}
 */
var swapPairs = function(head) {
    const dummy = new ListNode();
    
    dummy.next = head;
    let current = dummy;
    
    while (current) {
        const first = current.next;
        if (!first) {
            break
        }
        const second = first.next;
        if (!second) {
            break;
        }
        const third = second.next;
        
        current.next = second;
        second.next = first;
        first.next = third;
        current = first
        
    }
    
    return dummy.next;
};