题解 | 两个链表的第一个公共结点

/*
struct ListNode {
	int val;
	struct ListNode *next;
	ListNode(int x) :
			val(x), next(NULL) {
	}
};*/
#include <unordered_set>
class Solution {
public:
    ListNode* FindFirstCommonNode( ListNode* pHead1, ListNode* pHead2) {
        if(pHead1==nullptr&&pHead2==nullptr)
		{
			return NULL;
		}
		std::unordered_set<ListNode*> visited;
		while(pHead1!=nullptr) {visited.insert(pHead1);pHead1=pHead1->next;}

		while(pHead2!=nullptr)
		{
			if(visited.find(pHead2)!=visited.end())
			{
				return pHead2;
			}
			visited.insert(pHead2);
			pHead2=pHead2->next;
		}
		return NULL;	
    }
};