leetcode 【 Intersection of Two Linked Lists 】python 实现

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

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    # @param two ListNodes
    # @return the intersected ListNode
    def getListLen(self,head):
        length = 0
        while head is not None:
            length += 1
            head = head.next
        return length
            
    def getIntersectionNode(self, headA, headB):
        if headA is None or headB is None:
            return None
        
        hA = headA
        hB = headB
        
        lenA = self.getListLen(hA)
        lenB = self.getListLen(hB)
        
        if lenA > lenB :
            distance = lenA - lenB
            for i in range(0,distance):
                hA = hA.next
        if lenA < lenB :
            distance = lenB -lenA
            for i in range(0,distance):
                hB = hB.next
        
        intersection = None
        while hA is not None and hB is not None:
            if hA == hB:
                return hA
            else:
                hA = hA.next
                hB = hB.next
        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