2022-06-28

24. Swap Nodes in Pairs

Description

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

Solution

Approach #0

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func swapPairs(head *ListNode) *ListNode {
    cur := head
    for cur != nil && cur.Next != nil {
        next := cur.Next
        cur.Val, next.Val = next.Val, cur.Val
        cur = next.Next
    }
    return head
}