PattySung

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]

<解題>


class Solution {
    public ListNode swapPairs(ListNode head) {
        if (head == null || head.next == null) return head;

        ListNode dummy = new ListNode(0);
        ListNode curr = dummy;
        dummy.next= head;

        while (curr.next != null && curr.next.next != null){
            ListNode first = curr.next;
            ListNode second = curr.next.next;
            curr.next = second;
            first.next = second.next;
            second.next = first;
            curr = curr.next.next;
        }
        return dummy.next;
    }
}

Leetcode-24. Swap Nodes in Pairs

<解題>