【面试题】重排单链表

今天刷的小题一道，微软14年校园招聘笔试唯一一道编程题。

Given a singly linked list L: (L0 , L1 , L2...Ln-1 , Ln). Write a program to reorder it so that it becomes(L0 , Ln , L1 , Ln-1 , L2 , Ln-2...).

1 struct Node  

2 {  

3     int val_;  

4     Node* next;  

5 };

Notes:
1、Space Complexity should be O(1) 
2、Only the ".next" field of a node is modifiable.

代码：

 

 1 Node* ReorderList(Node* sll)

 2 {

 3     if(sll == NULL || sll->next == NULL || sll->next->next == NULL)

 4         return sll;

 5     Node* p1 = sll;

 6     Node* p2 = sll->next;

 7     Node* p3 = sll;

 8     Node* p4 = sll->next;

 9     while(p4->next != NULL)

10     {

11         p3 = p3->next;

12         p4 = p4->next;

13     }

14     while(p2->next != NULL)

15     {

16         p1->next = p4;

17         p4->next = p2;

18         p3->next = NULL;

19         p1 = p2;

20         p2 = p2->next;

21         p4 = sll;

22         while(p4->next != p3)

23             p4 = p4->next;

24         p3 = p4;

25         p4 = p4->next;

26         if(p2 == NULL)

27             break;

28     }

29     return sll;

30 }

View Code

自己多动手没坏处~