两个链表的第一个公共结点

需要先遍历一遍链表

8/FindFirstCommonNode.h

@@ -0,0 +1,60 @@
+#include<iostream>
+using namespace std;
+#include<vector>
+
+
+
+
+struct ListNode {
+int val;
+struct ListNode *next;
+ListNode(int x) :
+val(x), next(NULL) {
+}
+};
+
+
+int LengthAndTail(ListNode* cur, ListNode*& tail)
+{
+	typedef ListNode Node;
+	int count = 0;
+
+	while (cur->next !=NULL)
+	{
+		count++;
+		cur = cur->next;
+	}
+	tail = cur;
+	return count;
+}
+
+ListNode* FindFirstCommonNode(ListNode *pHead1, ListNode *pHead2) 
+{
+	typedef ListNode Node;
+	if (pHead1 == NULL || pHead2 == NULL) return NULL;
+
+	Node* cur1 = pHead1,*cur2 = pHead2;
+
+	Node* tail1 = NULL, *tail2 = NULL;
+	int length1= LengthAndTail(pHead1, tail1);
+	int length2 = LengthAndTail(pHead2, tail2);
+	if (tail1 != tail2)
+		return NULL;
+
+	Node* fast = length1 > length2 ? pHead1 : pHead2;
+	Node* slow = length1 > length2 ? pHead2 : pHead1;
+	int dif = length1 - length2;
+	while (dif)
+	{
+		fast = fast->next;
+		dif--;
+	}
+	while (fast&&slow)
+	{
+		if (fast == slow)
+			break;
+		fast = fast->next;
+		slow = slow->next;
+	}
+	return fast;
+}