/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public int length (ListNode head ){
        ListNode curr = head;
        int count = 0;
 
        while(curr!=null){
            count++;
            curr = curr.next;
        }
        return count;
    }
    public ListNode answer(ListNode headA, ListNode headB,int diff) {
 
        ListNode curr1 = headA;
        ListNode curr2 = headB;
 
        while(diff > 0){
            curr1 = curr1.next;
            diff--;
        }
 
        while(curr1 != null){
            if(curr1 == curr2)
            return curr1;
 
            curr1 = curr1.next;
            curr2 = curr2.next;
            
        }
        return null;
    }
 
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if(headA == null || headB == null)
        return null;
        
        //find length of LL
        int len1 = length(headA);
        int len2 = length(headB);
        int diff = 0;
        
        //then find difference
        diff  = Math.max(len1,len2) - Math.min(len1,len2);
 
        
        //skip no. of diff nodes from larger LL and start comparing one by one
        if(len1 >= len2)
            return answer( headA,  headB,diff);
 
        else 
        return answer( headB , headA,diff);
        
    }
}