求两个链表的第一个公共节点（建模有趣）

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) :
            val(x), next(NULL) {
    }
};*/
class Solution {
public:
    ListNode* FindFirstCommonNode( ListNode* pHead1, ListNode* pHead2) {
        ListNode* p1 = pHead1;
        ListNode* p2 = pHead2;
        while(p1 != p2)
        {
            p1 = (p1 == NULL ? pHead2 : p1 -> next);
            p2 = (p2 == NULL ? pHead1 : p2 -> next);
        }
        return p1;
    }
};