Description
Given a linked list, swap every two adjacent nodes and return its head.
Example
Given 1->2->3->4
, you should return the list as 2->1->4->3
.
Challenge
Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.
解题:将链表中的结点换一下位置。代码如下:
/**
* Definition for ListNode
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
/**
* @param head: a ListNode
* @return: a ListNode
*/
public ListNode swapPairs(ListNode head) {
// write your code here
ListNode dummy = new ListNode(-1);
dummy.next = head;
ListNode pre = dummy;
while(pre.next != null && pre.next.next != null){
ListNode t = pre.next.next;
pre.next.next = t.next;
t.next = pre.next;
pre.next = t;
pre = t.next;
}
return dummy.next;
}
}