LeetCode

Problem Statement

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

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func swapPairs(head *ListNode) *ListNode {
  dummy := ListNode{}
  dummy.Next = head

  pre := &dummy

  for pre != nil {
    if pre.Next == nil || pre.Next.Next == nil {
      break
    }

    first := pre.Next
    pre.Next = first.Next
    first.Next = first.Next.Next
    pre.Next.Next = first
    pre = first
  }

  return dummy.Next
}

Reference: