DSA-Java-Leetcode/143. Reorder List at main · risitadas/DSA-Java-Leetcode · GitHub

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution
{

    public ListNode func(ListNode slow , ListNode fast)
    {

        if(fast==null)
        {
            ListNode temp = slow.next;
            slow.next=null;

            return temp;

        }
        else if(fast.next==null)
        {

            ListNode temp =slow.next.next;
            slow.next.next=null;

            return temp;
        }
        else
        {

            ListNode temp = func(slow.next , fast.next.next);

            ListNode temp1 = slow.next;
            ListNode temp2 = temp.next;

            slow.next=temp;
            temp.next=temp1;


            return temp2;
        }


    }


    public void reorderList(ListNode head)
    {

        func(head, head.next);


    }


}