1 struct ListNode {
2 int val;
3 ListNode *next;
4 ListNode(int x) : val(x), next(nullptr) {}
5 };
6
7 ListNode* median(ListNode *head)
8 {
9 if(head != nullptr && head->next != nullptr)
10 {
11 ListNode *m = head;
12 ListNode *last = m->next;
13 while(last->next != nullptr)
14 {
15 if((last = last->next) != nullptr) last = last->next;
16 else break;
17 m = m->next;
18 }
19 return m;
20 }
21 else return head;
22 }
23
24 ListNode* advance_aux(ListNode *head, int len)
25 {
26 while(--len > 0) head = head->next;
27 return head;
28 }
29
30 ListNode** merge_aux(ListNode **l_head, ListNode **r_head, int l_len, int r_len)
31 {
32 cout<<"merge "
33 <<(*l_head)->val<<' '<<l_len<<" and "
34 <<(*r_head)->val<<' '<<r_len<<'\n';
35 ListNode **left = l_head, **right = r_head;
36 while(l_len != 0 && r_len != 0)
37 {
38 while(r_len != 0 && (*right)->val < (*left)->val)
39 {
40 right = &(*right)->next;
41 --r_len;
42 }
43 if(*right == *r_head)
44 {
45 while(l_len != 0 && (*left)->val <= (*right)->val)
46 {
47 left = &(*left)->next;
48 --l_len;
49 }
50 }
51 else
52 {
53 cout<<"\tmove ["
54 <<(*r_head)->val<<","
55 <<(r_len ? (*right)->val : -1)
56 <<") before "
57 <<(*left)->val<<"\n";
58 ListNode *tmp = *left;
59 *left = *r_head;
60 *r_head = *right;
61 *right = tmp;
62 left = &tmp->next;
63 --l_len;
64 right = r_head;
65 }
66 }
67 while(r_len-- != 0)
68 {
69 ListNode *tmp = *left;
70 *left = *r_head;
71 *r_head = *right;
72 *right = tmp;
73 }
74 return l_head;
75 }
76
77 ListNode** insertionSortList_aux(ListNode **head, int len)
78 {
79 cout<<"deal "<<(*head)->val<<' '<<len<<'\n';
80 if(len > 2)
81 {
82 int left_len = len/2, right_len = len - left_len;
83 head = insertionSortList_aux(head, left_len);
84 ListNode *left_last = advance_aux(*head, left_len);
85 ListNode **right_head = insertionSortList_aux(&left_last->next, right_len);
86 head = merge_aux(head, right_head, left_len, right_len);
87 }
88 else if(len == 2)
89 {
90 if((*head)->val > (*head)->next->val)
91 {
92 int tmp = (*head)->val;
93 (*head)->val = (*head)->next->val;
94 (*head)->next->val = tmp;
95 }
96 }
97 return head;
98 }
99
100 ListNode* insertionSortList(ListNode *head)
101 {
102 int len = 0;
103 ListNode *last = head;
104 while(last != nullptr)
105 {
106 ++len;
107 last = last->next;
108 }
109 insertionSortList_aux(&head, len);
110 return head;
111 }
112
113 ListNode* insertNode(ListNode *head, int i)
114 {
115 auto p = new ListNode{i};
116 p->next = head;
117 return p;
118 }
119
120 int main()
121 {
122 ListNode *p = nullptr;
123 p = insertNode(p, 0);
124 p = insertNode(p, 0);
125 p = insertNode(p, 0);
126 p = insertNode(p, 0);
127 for(ListNode *i = p; i != nullptr; i = i->next) cout<<i->val<<" ";
128 cout<<endl;
129 p = insertionSortList(p);
130 for(ListNode *i = p; i != nullptr; i = i->next) cout<<i->val<<" ";
131 cout<<endl;
132 while(p != nullptr)
133 {
134 ListNode *tmp = p->next;
135 delete p;
136 p = tmp;
137 }
138 }
