Swap Nodes in Pairs

Description

Given a linked list, swap every two adjacent nodes and return its head.

You may not modify the values in the list's nodes, only nodes itself may be changed.

 

Example:

Given 1->2->3->4, you should return the list as 2->1->4->3.

Solution(javascript)

function ListNode(val) {
  this.val = val
  this.next = null
}

const swapPairs = (head) => {
  const newHead = new ListNode(0)
  newHead.next = head
  let current = newHead
  while (
    current
    && current.next
    && current.next.next
  ) {
    const temp = current.next
    current.next = current.next.next
    const { next } = current.next
    current.next.next = temp
    temp.next = next
    current = current.next.next
  }
  return newHead.next
}