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) {
	}
};*/
class Solution {
public:
    ListNode* FindFirstCommonNode( ListNode* pHead1, ListNode* pHead2) {
		if(pHead1 == nullptr || pHead2 == nullptr){
			return nullptr;
		}
        ListNode *cur1=pHead1;
        ListNode *cur2=pHead2;
		int n=0;
		while(cur1->next ){
			cur1 = cur1->next;
			n++;
		}
		while(cur2->next ){
			cur2 = cur2->next;
			n--;
		}
		if(cur1 != cur2){
			return nullptr;
		}
		cur1 = n>0 ? pHead1:pHead2;
		cur2 = cur1==pHead1?pHead2:pHead1;
		n = abs(n);
		while(n){
			cur1=cur1->next;
			n--;
		}
		while(cur1 != cur2){
			cur1 = cur1->next;
			cur2 = cur2->next;
		}
		return cur1;
	}
};