题目描述：以给定值x为基准将链表分割成两部分，所有小于x的节点排在大于等于x的节点之前。

思路：设置largehead,largetail和smallhead,smalltail，第一次找到小于或者大于等于x的节点时就更新head指针，后面遍历链表每次更新tail指针。

实现没考虑空链表等边界情况。

 1 #include <iostream>
 2 #include <string>
 3 #include <fstream>
 4 #include <map>
 5 #include <algorithm>
 6 #include <vector>
 7 #include <ctime>
 8 #include <bitset>
 9 
10 using namespace std;
11 
12 template<typename T>
13 class Node
14 {
15 public:
16     Node<T> *next;
17     T data;
18 
19     Node(T d):data(d),next(NULL){}
20     void appendToTail(T d)
21     {
22         Node<T> *end = new Node<T>(d);
23         Node<T> *n = this;
24         while(n->next != NULL)
25         {
26             n = n->next;
27         }
28         n->next = end;
29     }
30 };
31 
32 int main()
33 {
34     Node<int> *head = new Node<int>(1);
35     int i;
36     head->appendToTail(4);
37     for(i = 2 ; i < 6 ; ++i)
38     {
39         head->appendToTail(i);
40     }
41     //2.4
42     head->appendToTail(4);
43     head->appendToTail(3);
44     Node<int> *largeHead = NULL;
45     Node<int> *largeTail = NULL;
46     Node<int> *smallHead = NULL;
47     Node<int> *smallTail = NULL;
48     Node<int> *headOrg = head;
49     int x = 3;
50     while(head != NULL)
51     {
52         if(head->data >= x)
53         {
54             if(largeHead == NULL)
55             {
56                 largeHead = head;
57                 largeTail = head;
58             }
59             else
60             {
61                 largeTail->next = head;
62                 largeTail = head;
63             }
64         }
65         else
66         {
67             if(smallHead == NULL)
68             {
69                 smallHead = head;
70                 smallTail = head;
71             }
72             else
73             {
74                 smallTail->next = head;
75                 smallTail = head;
76             }
77         }
78         head = head->next;
79     }
80     smallTail->next = largeHead;
81     while(smallHead != NULL)
82     {
83         cout<<smallHead->data<<endl;
84         smallHead = smallHead->next;
85     }
86     return 0;
87 }