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 ListNode 10 def getListLen(self,head): 11 length = 0 12 while head is not None: 13 length += 1 14 head = head.next 15 return length 16 17 def getIntersectionNode(self, headA, headB): 18 if headA is None or headB is None: 19 return None 20 21 hA = headA 22 hB = headB 23 24 lenA = self.getListLen(hA) 25 lenB = self.getListLen(hB) 26 27 if lenA > lenB : 28 distance = lenA - lenB 29 for i in range(0,distance): 30 hA = hA.next 31 if lenA < lenB : 32 distance = lenB -lenA 33 for i in range(0,distance): 34 hB = hB.next 35 36 intersection = None 37 while hA is not None and hB is not None: 38 if hA == hB: 39 return hA 40 else: 41 hA = hA.next 42 hB = hB.next 43 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