/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
public class Solution {
public ListNode swapPairs(ListNode head) {
if(head == null || head.next == null){
return head;
}
ListNode toReturn = head;
ListNode first = head;
ListNode second = head.next;
while(second != null){
int temp = first.val;
first.val = second.val;
second.val = temp;
if(second.next == null) return toReturn;
first = first.next.next;
second = second.next.next;
}
return toReturn;
}
}
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
public class Solution {
public ListNode swapPairs(ListNode head) {
ListNode dummy = new ListNode(0);
dummy.next = head;
ListNode cur = dummy;
while (cur.next != null && cur.next.next != null) {
ListNode first = cur.next;
ListNode second = cur.next.next;
first.next = second.next;
second.next = first;
cur.next = second;
cur = cur.next.next;
}
return dummy.next;
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
public class Solution {
public ListNode swapPairs(ListNode head) {
if (head == null || head.next == null) return head;
ListNode n = head.next;
head.next = swapPairs(head.next.next);
n.next = head;
return n;
}
}