在 C++ 中使用链表按字母顺序对字符串进行排序
Posted
技术标签:
【中文标题】在 C++ 中使用链表按字母顺序对字符串进行排序【英文标题】:sort strings in alphabetical order with linked lists in c++ 【发布时间】:2017-04-06 05:15:09 【问题描述】: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)
返回按字母顺序排在第一位的字符串。
这个功能很好用。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,我必须删除 minimum(string)
函数返回的字符串。我遇到问题的函数是sort()
。
它要我定义一个StringNode
指针作为新列表(空列表)的头部,然后我需要一个循环,在其中调用minimum(string)
和remove(string)
的函数。在循环内部,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)。旧的头指针(现在为空)必须指向新的列表。
我对此很困惑,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,这将是一个空列表,意思是newList->next = NULL;
然后在循环中我需要创建另一个新节点,以及一个指向内部新节点头部的指针循环。我需要将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!
这是打洞程序。
// StringList.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
//Driver.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();
【问题讨论】:
【参考方案1】:您的删除功能有小故障。您没有考虑删除第一个节点的可能性。
bool StringList::remove(string movie)
StringNode *p = head;
StringNode *n = NULL;
if(p->data==movie) //added this condition
head=head->next;
delete p;
return true;
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;
最终排序函数。目标是使用 minimum 和 remove 函数对现有列表进行排序,并获得新的排序列表。您需要从现有列表中获取最小值并继续将它们添加到新列表的末尾。最后更改头指针以将其指向新列表。
while 循环应该一直运行到现有列表变为空为止。
void StringList::sort()
string mini;
bool removed;
//adding the first node to the new list.
StringNode *newnode1 = new StringNode;
mini = minimum(); // get the minimum from the existing linked list
newnode1->data = mini;
newnode1->next = NULL;
removed =remove(mini);
StringNode *p = newnode1;
while (head != NULL) // the loop should run until the original list is empty
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
removed = remove(mini);
p=p->next;
head=newnode1; //finally change the head pointer, so that the head now points to sorted list.
【讨论】:
以上是关于在 C++ 中使用链表按字母顺序对字符串进行排序的主要内容,如果未能解决你的问题,请参考以下文章