题解 | #两个链表的第一个公共结点#

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

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode FindFirstCommonNode(ListNode pHead1, ListNode pHead2) {
        //将两个列表同时往哈希表里塞
        //如果都塞完了，还没有一样的，说明没有相交点
        HashSet<ListNode> nodes = new HashSet<>();
        ListNode result = null;
        while(pHead1 != null){
            if(nodes.contains(pHead1)){
                return pHead1;
            }
            nodes.add(pHead1);
            pHead1 = pHead1.next;
            if(pHead2 != null){
                if(nodes.contains(pHead2)){
                    return pHead2;
                }
                nodes.add(pHead2);
                pHead2 = pHead2.next;
            }
        }
        return result;
    }
}