单链表快速排序

Posted 2020-08-06 LC凑热闹

详细解释在代码中，主要思路是将链表分为三个部分，小于key的链表，等于key的链表，大于key的链表

  1 #include <iostream>
  2 #include<string>
  3 #include <vector>
  4 #include <algorithm>
  5 using namespace std;
  6 
  7 class node
  8 {
  9 public:
 10     int value;
 11     node *next;
 12     node():value(0),next(NULL)
 13     {
 14     }
 15     node(int val):value(val),next(NULL)
 16      {
 17      }
 18 };
 19 
 20 void LinkQuickSort(node*&head)
 21 {
 22     if (NULL == head->next )
 23     {
 24         return;
 25     }
 26     const int key = head->value;
 27     //将链表拆分为三部分
 28     node *left = new node;//小于key的链表伪头结点
 29     node *right = new node;//大于key的链表伪头结点
 30     node *middle = head;//等于key的链表头结点
 31 
 32     node *lastLeft,*lastRight,*temp,*lastMiddle;
 33     lastRight = right;//记录链表最后一个节点
 34     lastLeft = left;
 35     lastMiddle = middle;    
 36     
 37     temp=head->next;//从第二个元素开始
 38     lastMiddle->next = NULL;
 39     while(NULL != temp)
 40     {
 41         if((temp->value)> key)
 42         {
 43             lastRight->next = temp;
 44             lastRight = lastRight->next;
 45             temp = temp->next;
 46             lastRight->next=NULL;
 47         }
 48         else if ((temp->value) < key)
 49         {
 50             lastLeft->next = temp;
 51             lastLeft = lastLeft->next;
 52             temp = temp->next;
 53             lastLeft->next=NULL;
 54         }
 55         else
 56         {
 57             lastMiddle->next = temp;
 58             lastMiddle = lastMiddle->next;
 59             temp = temp->next;
 60             lastMiddle->next=NULL;
 61         }
 62     }
 63     temp = left;
 64     left = left->next;
 65     temp->next = NULL;
 66     delete temp;//删除伪头结点
 67 
 68     temp = right;
 69     right = right->next;
 70     temp->next = NULL;
 71     delete temp;
 72 
 73     if(NULL != left)
 74         LinkQuickSort(left);
 75     if (NULL != right)
 76         LinkQuickSort(right);
 77 
 78     //合并三个链表
 79     
 80     if (NULL != left)//做链表不为空
 81     {
 82         temp = left;
 83         head = left;
 84         while(temp->next!=NULL)//定位最后一个节点
 85         {
 86             temp = temp->next;
 87         }
 88         temp->next = middle;
 89     }
 90     else
 91     {
 92         head = middle;
 93     }
 94 
 95     lastMiddle->next = right;//right 为NULL也无所谓
 96     
 97 }
 98 
 99 int main()
100 {
101     node *head=new node;
102 
103     node *temp = head;
104     temp->next = new node(5);
105     temp = temp->next;
106     temp->next = new node(19);
107     temp = temp->next;
108 
109     temp->next = new node(19);
110     temp = temp->next;
111 
112     temp->next = new node(22);
113     temp = temp->next;
114 
115     temp->next = new node(44);
116     temp = temp->next;
117 
118     temp = head;
119     head = head->next;
120     temp->next = NULL;
121     delete temp;
122 
123     LinkQuickSort(head);
124 
125     temp = head;
126     while(temp!=NULL)
127     {
128         cout << temp->value <<" ";
129         temp = temp->next;
130     }
131     cout << endl;
132 
133     return 0;
134 }