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Leetcode 160. Intersection of two linked lists
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.
Notes:
- If the two linked lists have no intersection at all, return
null
. - The linked lists must retain their original structure after the function returns.
- You may assume there are no cycles anywhere in the entire linked structure.
- Your code should preferably run in O(n) time and use only O(1) memory.
1 class Solution(object): 2 def getIntersectionNode(self, headA, headB): 3 """ 4 :type head1, head1: ListNode 5 :rtype: ListNode 6 """ 7 8 n = self.getLength(headA) 9 m = self.getLength(headB) 10 11 if n < m: 12 return self.getIntersectionNode(headB, headA) 13 14 for i in range(n-m): 15 headA = headA.next 16 17 while headA and headB: 18 if id(headA) == id(headB): 19 return headA 20 headA = headA.next 21 headB = headB.next 22 return None 23 24 def getLength(self, head): 25 n = 0 26 while head: 27 head = head.next 28 n += 1 29 return n
1. 总是先操作长度较短的那个list.
2. 用id(headA) == id(headB) 判断两个node是不是一样
Leetcode 160. Intersection of two linked lists
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