HackerHeap

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.

Solution 1:

public class Solution {
    public ListNode swapPairs(ListNode head) {
        if(head == null || head.next == null) return head;
        int count = 1;
           ListNode current = head;
           ListNode temp = head;
           ListNode returnNode = head.next;
           while(current.next!=null){
               if(getNextNode(current)!=null && count == 1){
               ListNode nextNode = getNextNode(current);
               current.next = nextNode.next;
               nextNode.next = current;
               temp = current;
               if(current.next!=null){
               current = current.next;
               }
               count++;
               }else if(getNextNode(current)!=null && count > 1){
                   ListNode nextNode = getNextNode(current);
               current.next = nextNode.next;
               nextNode.next = current;
               temp.next  = nextNode;
               temp = current;
               if(current.next!=null){
               current = current.next;
               }
               }
               
           }
           return returnNode;
               
    }
    
    public ListNode getNextNode(ListNode head){
        return head.next;
    }
}