import ListNodeInfo.ListNode;

import java.util.HashSet;
import java.util.Set;

public class Problem_160_IntersectionOfTwoLinkedList {
    //双指针方法 
    public ListNode getIntersectionListNode(ListNode headA, ListNode headB){
        if(headA == null || headB == null) return null;
        ListNode a = headA;
        ListNode b = headB;
        while (a != b){
            a = a == null ? headB : a.next;
            b = b == null ? headA : b.next;
        }
        return a;
    }
    //利用set方法
    public ListNode getIntersectionListNode1(ListNode headA, ListNode headB){
        if(headA == null || headB == null)return null;
        Set<ListNode> set = new HashSet<>();
        while (headA != null){
            set.add(headA);
            headA = headA.next;
        }
        while (headB != null){
            if(set.contains(headB))return headB;
            headB = headB.next;
        }
        return null;
    }
}