码迷,mamicode.com
首页 > 其他好文 > 详细

leetcode-160-Intersection of Two Linked Lists

时间:2015-07-25 10:46:05      阅读:118      评论:0      收藏:0      [点我收藏+]

标签:leetcode   链表   

                                   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.
求两个链表的相交处的节点。不想交则返回NULL。

若两链表相交,则它们的后半部分一定相同。将两链表的后半部分对齐,即先将长的链表往后走,直到与短的链表长度一样,开始遍历两链表,找到的第一个相同的节点就是相交处的节点。
C++
/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {
        int nA = 0,nB = 0,n;// 链表长度
        ListNode* p;
        
        p = headA; //headA的长度nA
        while (p) {
            nA++;
            p = p->next;
        }
        p = headB; //headB的长度nB
        while (p) {
            nB++;
            p = p->next;
        }
    
        if (nA < nB) {
            n = nB - nA;
            while (n--) headB = headB->next;
        } 
        else if (nA > nB) {
            n = nA - nB;
            while (n--) headA = headA->next;
        }
        
        while (headA && headB) {
            if (headA == headB) return headA;
            headA = headA->next;
            headB = headB->next;
        }
        return NULL;
    }
};


python
# 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 getIntersectionNode(self, headA, headB):
        nA = nB = 0
        p = headA
        while (p is not None) :
            nA = nA + 1
            p = p.next
        p = headB
        while (p is not None) :
            nB = nB + 1
            p = p.next
        
        if (nA < nB) :
            n = nB - nA
            while (n) :
                headB = headB.next
                n = n - 1
        elif (nA > nB) :
            n = nA - nB
            while (n) :
                headA = headA.next
                n = n - 1
        
        while (headA  and headB ) :
            if (headA == headB):
                return headA
            headA = headA.next
            headB = headB.next
        
        return None



版权声明:本文为博主原创文章,未经博主允许不得转载。

leetcode-160-Intersection of Two Linked Lists

标签:leetcode   链表   

原文地址:http://blog.csdn.net/u014705854/article/details/47053169

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!