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) {
        ListNode* h1 = pHead1;
		ListNode* h2 = pHead2;
		int L1 = 0;
		int L2 = 0;
		int m;
	  //计算链表1长度
		while(h1){
			L1++;
			h1 = h1->next;
		}
	  //计算链表2长度
		while(h2){
			L2++;
			h2 = h2->next;
		}
		//长的链表先移动|L1-L2|
		h1 = pHead1;
		h2 = pHead2;
		if(L1>=L2){
			m = L1 - L2;
			while(m--){
				h1 = h1->next;
			}
		}else{
			m = L2 - L1;
			while(m--){
				h2 = h2->next;
			}
		}
	  	//同步比较，直到找出第一个相同节点
		while(h1 != h2){
			h1 = h1->next;
			h2 = h2->next;
		}
		return h1;
    }
};