在LinkedLists上執行mergeSort

Question

我被分配編寫一個項目，該項目在某種程度上可以模擬機場的時間表。 這必須使用linkedLists實現。 該項目應由Node類和SLL（單鏈表）類組成。 項目的邏輯是這樣的：在主功能中應該有一個時鍾，每15分鍾滴答一次。 我創建了flight.h文件，並在其中包含了與航班有關的所有信息。 讓我感到困惑的只是與mergeSort和quickSort相關的部分代碼。 該項目要求對所有航班進行排序：1.根據出發時間2.基於出發城市。

#include <stdlib.h>
#include <string>
#include <ctime>

using namespace std;

#ifndef FLIGHT_H_
#define FLIGHT_H_

class Node
{
public:
    Node()
    {
        flightNum = 0;
        gate = 0;
        status = On_time;
        next = NULL;
    }
    enum Flight_status {On_time, Delayed, Departed};
    struct Time {int hour, minutes;}; time;
    string airLine;
    int flightNum;
    string city;
    int gate;
    Flight_status status;
    Node *next;
    friend class SLL;
};

class SLL
{
private:
    Node *head;
    Node *tail;
    int size;
public:
    SLL() {head = tail = NULL; size = 0;}
    ~SLL() {};
    // Member function to add a new Node into a list
    void addNode();
    // Member functions to perform mergeSort over the list
    void split(SLL *, int, int);
    void merge(SLL *, int, int, int);
    // Member functions to perform quickSort over the list
    void partition(SLL *, int, int);
    void swap(Node &, Node &);
    void quickSort(SLL *, int, int);
    //
    void display(SLL *);
};

#endif /* FLIGHT_H_ */

我正在考慮在此聲明之上構建程序的其余部分。 根據類的這種實現，我想確定的是我解決排序問題的方法是好的。 如果您在實施此項目時遇到任何問題，請幫助我。 提前致謝。

Answer 1

這是代碼。.根據您的問題進行修改。

#include<stdio.h>
#include<stdlib.h>

/* Link list node */
struct node
{
    int data;
    struct node* next;
};

/* function prototypes */
struct node* SortedMerge(struct node* a, struct node* b);
void FrontBackSplit(struct node* source,
          struct node** frontRef, struct node** backRef);

/* sorts the linked list by changing next pointers (not data) */
void MergeSort(struct node** headRef)
{
  struct node* head = *headRef;
  struct node* a;
  struct node* b;

  /* Base case -- length 0 or 1 */
  if ((head == NULL) || (head->next == NULL))
  {
    return;
  }

  /* Split head into 'a' and 'b' sublists */
  FrontBackSplit(head, &a, &b); 

  /* Recursively sort the sublists */
  MergeSort(&a);
  MergeSort(&b);

  /* answer = merge the two sorted lists together */
  *headRef = SortedMerge(a, b);
}

struct node* SortedMerge(struct node* a, struct node* b)
{
  struct node* result = NULL;

  /* Base cases */
  if (a == NULL)
     return(b);
  else if (b==NULL)
     return(a);

  /* Pick either a or b, and recur */
  if (a->data <= b->data)
  {
     result = a;
     result->next = SortedMerge(a->next, b);
  }
  else
  {
     result = b;
     result->next = SortedMerge(a, b->next);
  }
  return(result);
}

/* UTILITY FUNCTIONS */
/* Split the nodes of the given list into front and back halves,
     and return the two lists using the reference parameters.
     If the length is odd, the extra node should go in the front list.
     Uses the fast/slow pointer strategy.  */
void FrontBackSplit(struct node* source,
          struct node** frontRef, struct node** backRef)
{
  struct node* fast;
  struct node* slow;
  if (source==NULL || source->next==NULL)
  {
    /* length < 2 cases */
    *frontRef = source;
    *backRef = NULL;
  }
  else
  {
    slow = source;
    fast = source->next;

    /* Advance 'fast' two nodes, and advance 'slow' one node */
    while (fast != NULL)
    {
      fast = fast->next;
      if (fast != NULL)
      {
        slow = slow->next;
        fast = fast->next;
      }
    }

    /* 'slow' is before the midpoint in the list, so split it in two
      at that point. */
    *frontRef = source;
    *backRef = slow->next;
    slow->next = NULL;
  }
}

/* Function to print nodes in a given linked list */
void printList(struct node *node)
{
  while(node!=NULL)
  {
   printf("%d ", node->data);
   node = node->next;
  }
}

/* Function to insert a node at the beginging of the linked list */
void push(struct node** head_ref, int new_data)
{
  /* allocate node */
  struct node* new_node =
            (struct node*) malloc(sizeof(struct node));

  /* put in the data  */
  new_node->data  = new_data;

  /* link the old list off the new node */
  new_node->next = (*head_ref);    

  /* move the head to point to the new node */
  (*head_ref)    = new_node;
} 

/* Drier program to test above functions*/
int main()
{
  /* Start with the empty list */
  struct node* res = NULL;
  struct node* a = NULL;

  /* Let us create a unsorted linked lists to test the functions
   Created lists shall be a: 2->3->20->5->10->15 */
  push(&a, 15);
  push(&a, 10);
  push(&a, 5); 
  push(&a, 20);
  push(&a, 3);
  push(&a, 2); 

  /* Sort the above created Linked List */
  MergeSort(&a);

  printf("\n Sorted Linked List is: \n");
  printList(a);           

  getchar();
  return 0;
}

資料來源： http : //en.wikipedia.org/wiki/Merge_sort
http://cslibrary.stanford.edu/105/LinkedListProblems.pdf
http://www.geeksforgeeks.org/merge-sort-for-linked-list/