在 C++ 中使用链表按字母顺序对字符串进行排序

我正在分配字符串的链表。在我进入排序部分之前，一切似乎都很好。我也在使用类。我已经有 2 个功能。第一个minimum(string)它返回按字母顺序排在第一位的字符串的位置。

此功能工作正常。我还有一个函数remove(string)它从链表中删除包含给定字符串的节点。如果成功，则返回 true，否则返回 false(如果字符串不在列表中)，在这种情况下，我必须擦除minimum(string)函数返回的字符串。我遇到麻烦的功能是sort()。

它希望我定义一个StringNode指针作为新列表(空列表)的头部，然后我需要一个循环，我将在其中调用minimum(string)和remove(string)的函数。在循环中，我还需要将此节点插入到新列表中的正确位置(将其附加到末尾)。旧的头部指针(现在为空)必须指向新列表。

我对此感到非常困惑，到目前为止我有这个：

void StringList::sort()
{
StringNode *newList = new StringNode;
newList = NULL;
string mini;
bool removed;
while (newList->next != NULL)
{
StringNode *newList2 = new StringNode;
StringNode *p = head;
mini = minimum();
p->data = mini;
p->next = NULL;
newList2 = newList2->next;
newList2->next = p;
removed = remove(mini);
newList = newList2;
}
}

我的理解是：我需要创建一个新节点，它将是一个空列表，这意味着newList->next = NULL;然后在循环中我需要创建另一个新节点，以及一个指向循环内新节点头部的指针。我需要使最小值给出的值存储在指针p和指向新节点的指针中。

任何帮助将不胜感激。谢谢！

这是洞程序。

字符串列表.cpp

#include <iomanip>
#include <iostream>
#include <sstream>
#include "StringList.h"
using namespace std;
//******************************************************************************
// StringList: creates an empty list
//******************************************************************************
StringList::StringList()
{
head = NULL;
}
//******************************************************************************
// StringList: deallocates all the nodes in StringList
//******************************************************************************
StringList::~StringList()
{
StringNode *p;
StringNode *n;
p = head;
while (p != NULL)
{
n = p->next;
delete p;
p = n;
}
}
//******************************************************************************
// count: returns the total number of nodes in the list.
//******************************************************************************
int StringList::count()
{
int count = 0;
StringNode *p;
p = head;
while ( p != NULL )
{
count++;
p = p->next;
}
return count;
}
//******************************************************************************
// add: adds a new node to the beginning of the list.
//******************************************************************************
void StringList::add(string movie)
{
StringNode *newNode = new StringNode;
newNode->data = movie;
newNode->next = head;
head = newNode;
}
//******************************************************************************
// remove: removes a node containing the string from linked list
// returns true if successful or false the string is not in the list
//******************************************************************************
bool StringList::remove(string movie)
{
StringNode *p = head;
StringNode *n = NULL;
while (p != NULL && p->data != movie )
{
n = p;
p = p->next;
if (p == NULL )
{
return false;
}
else if (p->data == movie)
{
n->next = p->next;
delete p;
return true;
}
}
}
//******************************************************************************
//display: Displays the strings in the list.
//******************************************************************************
void StringList::display()
{
StringNode *p;
p = head;
while (p != NULL)
{
cout << p->data << " ";
p = p->next;
}
cout << endl;
}
//******************************************************************************
//minimum: return the string in alphabetical order
//******************************************************************************
string StringList::minimum()
{
StringNode *p = head;
string minimum = p->data;
while (p->next != NULL)
{
p = p->next;
if(minimum > p->data)
{
minimum = p->data;
}
}
return minimum;
}
//******************************************************************************
//sort: will call the minimum function and remove function
//******************************************************************************
void StringList::sort()
{
StringNode* newhead;  // create a new head pointer
string mini;
bool removed; 
//adding the first node to the new list.
StringNode *newnode = new StringNode;
mini = minimum();  // get the minimum from the existing linked list
newnode->data = mini; 
newnode->next = NULL;
newhead=newnode; //add the minimum node to the new list(with the newhead)
StringNode *p = newhead;
while (head != NULL) // loop should run until there's no node left in the original list
{
StringNode *newnode = new StringNode;
mini = minimum();  // get the minimum from the existing linked list
newnode->data = mini; 
newnode->next = NULL;
p->next=newnode; //add the minimum node to the new list(with the newhead pointer)
removed = remove(mini);
p=p->next;  
}
head=newhead; //finally change the head pointer, so that the head now points to sorted list.
}

StringList.h

#ifndef STRINGLIST_H_INCLUDED
#define STRINGLIST_H_INCLUDED
#include <string>
using namespace std;
class StringList
{
private:
struct StringNode          // the Nodes of the linked list
{
string data;           // data is a string
StringNode *next;      // points to next node in list
};
StringNode *head;           // the head pointer
public:
StringList();
~StringList();
int count();
void add(string);
bool remove(string);
void display();
string minimum();
void sort();
};

#endif // STRINGLIST_H_INCLUDED

驱动程序.cpp

#include<iostream>
#include<iomanip>
using namespace std;
#include "StringList.h"
int main()
{
//testing StringList
StringList slist;
string movie1 = "Star Wars";
string movie2 = "Fargo";
string movie3 = "Back to the Future";
string movie4 = "Titanic";
// Testing add/display/count
cout << "Testing add/display/count: " << endl;
cout << "count is: " << slist.count() << endl;
slist.add(movie1);
slist.display();
cout << "count is: " << slist.count() << endl;
slist.add(movie2);
slist.display();
cout << "count is: " << slist.count() << endl;
slist.add(movie3);
slist.add(movie4);
slist.display();
cout << "count is: " << slist.count() << endl;
// Testing remove
cout << endl;
cout << "Testing remove: " << endl;
bool delResult;
delResult = slist.remove(movie4);
cout << "remove result movie4 = " << boolalpha << delResult << endl;
delResult = slist.remove(movie3);
cout << "remove result movie3 = " << boolalpha << delResult << endl;
delResult = slist.remove("Not There");
cout << "remove result Not There = " << boolalpha << delResult << endl;
cout << "display after remove: " << endl;
slist.display();
cout << "count is: " << slist.count() << endl;
//Testing minimum
cout << endl;
cout << "Testing minimum: " << endl;
cout << "Test minimum 1: " << endl;
slist.display();
cout << "minimum: " << boolalpha << slist.minimum() << endl;
cout << "Test minimum 2: " << endl;
slist.add(movie4);
slist.display();
cout << "minimum: " << boolalpha << slist.minimum() << endl;
cout << "Test minimum 3: " << endl;
slist.add(movie3);
slist.display();
cout << "minimum: " << boolalpha << slist.minimum() << endl;
//Testing sort and display
cout << endl;
cout << "Testing sort/display: " << endl;
slist.sort();
slist.display();
cout << endl;
cout << "Testing sort/display after add: " << endl;
slist.add("Jurassic Park");
slist.display();
cout << "now sorted: " << endl;
slist.sort();
slist.display();

}