public class Solution {

     public ListNode getIntersectionNode(ListNode headA, ListNode headB) {

         if(headA==null||headB==null) return null;

         int lengthA=0;

         int lengthB=0;

         ListNode currentA=headA;

         ListNode currentB=headB;

         while(currentA.next!=null)

         {

             currentA=currentA.next;

             lengthA++;

         }

          while(currentB.next!=null)

         {

              currentB=currentB.next;

             lengthB++;

         }

         ListNode fast=lengthA>lengthB?headA:headB;

         ListNode slow=lengthA>lengthB?headB:headA;

         for(int i=0;i<Math.abs(lengthA-lengthB);i++)

         {

             fast=fast.next;

         }

         while(fast!=null)

         {

             if(fast==slow)

             return fast;

             else

             {

                 fast=fast.next;

                 slow=slow.next;

             }

         }

         return null;

     }

 }