https://leetcode.com/problems/intersection-of-two-linked-lists/description/

IntersectingListNode.java

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

class IntersectingListNode {
    public static void main(String[] args) {
        ListNode Anode5 = new ListNode(5);
        ListNode Anode4_2 = new ListNode(4, Anode5);
        ListNode Anode8 = new ListNode(8, Anode4_2);
        ListNode Anode1 = new ListNode(1, Anode8);
        ListNode Anode4 = new ListNode(4, Anode1);

        ListNode Bnode1 = new ListNode(1, Anode8);
        ListNode Bnode6 = new ListNode(6, Bnode1);
        ListNode Bnode5 = new ListNode(5, Bnode6);

        ListNode resultNode = new IntersectingListNode().getIntersectionNode(Anode4, Bnode5);
        printNode(resultNode);
    }

    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        ListNode resultNode = null;
        Map<Integer, List<ListNode>> elements = new HashMap<>();
        while((headA!=null || headB!=null) && resultNode==null){
            if(headA!=null){
                if(!elements.containsKey(headA.val)){
                    List<ListNode> nodes = new ArrayList<>();
                    nodes.add(headA);
                    elements.put(headA.val, nodes);
                }else{
                    List<ListNode> nodes = elements.get(headA.val);
                    for (int i = 0; i < nodes.size(); i++) {
                        if(nodes.get(i) == headA){
                            resultNode = headA;
                            break;
                        }
                    }
                    if(resultNode==null)
                        nodes.add(headA);
                }
                headA = headA.next;
            }

            if(headB!=null){
                if(!elements.containsKey(headB.val)){
                    List<ListNode> nodes = new ArrayList<>();
                    nodes.add(headB);
                    elements.put(headB.val, nodes);
                }else{
                    List<ListNode> nodes = elements.get(headB.val);
                    for (int i = 0; i < nodes.size(); i++) {
                        if(nodes.get(i) == headB){
                            resultNode = headB;
                            break;
                        }
                    }
                    if(resultNode==null)
                        nodes.add(headB);
                }
                headB = headB.next;
            }
        }
        return resultNode;
    }


    static void printNode(ListNode node){
        if(node==null){
            System.out.println("No common node found");
        }else{
            while(node!=null){
                System.out.print(node.val+" ");
                node=node.next;
            }
        }
    }
}

class ListNode {
 int val;
 ListNode next;
 ListNode(int x) {
     val = x;
     next = null;
 }

ListNode(int x, ListNode next) {
    val = x;
    this.next = next;
}
}