排序算法---链表排序

1 #include <iostream>
  2 
  3 using namespace std;
  4 
  5 struct Node
  6 {
  7     struct Node *next;
  8     int data;
  9 };
 10 
 11 Node *createNode(int x)
 12 {
 13     Node *p = NULL;
 14     
 15     p = new Node;
 16     p->next = NULL;
 17     p->data = x;
 18     
 19     return p;
 20 }
 21 
 22 void addNode(Node **head, Node *p)
 23 {
 24     Node *temp = NULL;
 25     if(*head == NULL)
 26     {
 27         *head = p;
 28     }
 29     else
 30     {
 31         temp = *head;
 32         while(temp->next != NULL)
 33         {
 34             temp = temp->next;
 35         }
 36         temp->next = p;
 37     }
 38 }
 39 
 40 void showList(Node *head)
 41 {
 42     while(head != NULL)
 43     {
 44         cout << head->data << "  ";
 45         head = head->next;
 46     }
 47     cout << endl;
 48 }
 49 
 50 void swap(int& a, int& b)
 51 {
 52     int tmp = b;
 53     b = a;
 54     a = tmp;
 55 }
 56 
 57 // 1. 直接选择排序   ------直接交换数据
 58 void ListSort_1(Node **head)
 59 {
 60     Node *p = NULL;
 61     Node *q = NULL;
 62     Node *t = NULL;
 63     
 64     if(*head == NULL || (*head)->next == NULL)
 65     {
 66         return;
 67     }
 68 
 69     for(p = *head; p != NULL; p = p->next)
 70     {
 71         t = p;
 72         
 73         for(q = p->next; q != NULL; q = q->next)
 74         {
 75             if(q->data < t->data)
 76             {
 77                 t = q;
 78             }
 79         }
 80         
 81         if(t != p)
 82         {
 83             swap(p->data, t->data);
 84         }
 85     }
 86     
 87     return;
 88 }
 89 
 90 // 2. 冒泡排序     ------直接交换数据
 91 void ListSort_2(Node **head)
 92 {
 93     Node *p = NULL;
 94     Node *q = NULL;
 95     Node *t = NULL;
 96     
 97     if(*head == NULL || (*head)->next == NULL)
 98     {
 99         return;
100     }
101 
102     for(p = *head; p != NULL; p = p->next)
103     {
104         for(q = *head; q->next != NULL; q = q->next)
105         {
106             if(q->data > q->next->data)
107             {
108                 swap(q->data, q->next->data);
109             }
110         }
111         
112     }
113 }
114 
115 // 3. 插入排序
116 void ListSort_3(Node **head)
117 {
118     //直接插入排序涉及到链表的反向遍历，比较麻烦，不建议
119 }
120 
121 Node *merge(Node *left, Node *right)
122 {
123     Node *head = createNode(-1);  // 小技巧
124     Node *temp = head;
125     
126     while(left != NULL && right != NULL)
127     {
128         if(left->data < right->data)
129         {
130             temp->next = left;
131             temp = temp->next;
132             left = left->next;
133         }
134         else
135         {
136             temp->next = right;
137             temp = temp->next;
138             right = right->next;
139         }
140     }
141     
142     if(left != NULL)
143     {
144         temp->next = left;
145     }
146     
147     if(right != NULL)
148     {
149         temp->next = right;
150     }
151     
152     return head->next;
153 }
154 
155 Node *_ListSort_4(Node *head)
156 {
157     Node *pFast = NULL;
158     Node *pSlow = NULL;
159     Node *mid = NULL;
160     
161     if(head == NULL || head->next == NULL)
162     {
163         return head;
164     }
165     
166     pFast = head;
167     pSlow = head;
168     
169     while(pFast->next != NULL && pFast->next->next != NULL)
170     {
171         pFast = pFast->next->next;
172         pSlow = pSlow->next;
173     }
174     
175     mid = pSlow->next;
176     pSlow->next = NULL;
177     
178     return merge(_ListSort_4(head), _ListSort_4(mid));
179 }
180 
181 // 4. 归并排序      ------交换节点
182 void ListSort_4(Node **head)
183 {
184     Node *temp = *head;
185     *head = _ListSort_4(temp);
186 }
187 
188 int main()
189 {
190     Node *head = NULL;
191     
192     addNode(&head, createNode(2));
193     addNode(&head, createNode(5));
194     addNode(&head, createNode(7));
195     addNode(&head, createNode(4));
196     addNode(&head, createNode(6));
197     addNode(&head, createNode(3));
198     addNode(&head, createNode(1));
199     addNode(&head, createNode(9));
200     addNode(&head, createNode(8));
201 
202     cout << "Sort Before:" << endl;
203     showList(head);
204     
205     //ListSort_1(&head);
206     //ListSort_2(&head);
207     ListSort_4(&head);
208     
209     cout << "Sort After:" << endl;
210     showList(head);211 
212     while(1);
213     return 0;
214 }