[leetcode]24. Swap Nodes in Pairs交换节点对

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.

题意：

给定一个链表，每两个节点做一下交换。

Solution1: Two Pointers(fast & slow)

(1) use Two Pointers(fast & slow) to find a pair

(2)swap

(3) move forward to find a new pair

code:

 /*

 Time: O(n)

 Space: O(1)

 */

 class Solution {

        public ListNode swapPairs(ListNode head) {

         ListNode dummy = new ListNode(-1);

         dummy.next = head;

         head = dummy;

         while (head.next != null && head.next.next != null) {

             // narrow to find a pair

             ListNode slow = head.next;

             ListNode fast = head.next.next;

             // swap

             head.next = fast;

             slow.next = fast.next;

             fast.next = slow;

             // move to next pair

             head = slow;

         }

         return dummy.next;

     }

 }

巴特西

[leetcode]24. Swap Nodes in Pairs交换节点对

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