题目：

Write a program to find the node at which the intersection of two singly linked lists begins.

 

For example, the following two linked lists: 

A:          a1 → a2                   ↘                     c1 → c2 → c3                   ↗            B:     b1 → b2 → b3

begin to intersect at node c1.

 

代码：oj在线测试通过 Runtime: 1604 ms

1 # Definition for singly-linked list. 2 # class ListNode: 3 #     def __init__(self, x): 4 #         self.val = x 5 #         self.next = None 6  7 class Solution: 8     # @param two ListNodes 9     # @return the intersected ListNode10     def getListLen(self,head):11         length = 012         while head is not None:13             length += 114             head = head.next15         return length16             17     def getIntersectionNode(self, headA, headB):18         if headA is None or headB is None:19             return None20         21         hA = headA22         hB = headB23         24         lenA = self.getListLen(hA)25         lenB = self.getListLen(hB)26         27         if lenA > lenB :28             distance = lenA - lenB29             for i in range(0,distance):30                 hA = hA.next31         if lenA < lenB :32             distance = lenB -lenA33             for i in range(0,distance):34                 hB = hB.next35         36         intersection = None37         while hA is not None and hB is not None:38             if hA == hB:39                 return hA40             else:41                 hA = hA.next42                 hB = hB.next43         return intersection

 

 

思路：

1. 首先要记录两个Linked List的长度

2. 双指针 分别指向两个List 指向长List的先走若干步,获得一个新的Linked List表头

3. 逐一比较两个List的每个指针的值是否相等：直到找到相等的，或者到None