set查找重复项

import java.util.*;
/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode FindFirstCommonNode(ListNode p1, ListNode p2) {
        Set<ListNode> set = new HashSet<>();
        while(p1 != null){
            set.add(p1);
            p1 = p1.next;
        }
        while(p2 != null && ! set.contains(p2)) p2 = p2.next;
        return p2;
    }
}