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我正在开发一个使用双向链表的程序。我已经获得了插入节点、删除节点、从节点检索值、显示列表、输出列表大小、判断列表是否为空以及删除所有节点的功能。

我遇到的问题是以升序对值进行排序，并找到某个值所在的节点。

我明天要去帮助实验室，我只是想在那之前看看是否有人可以提供帮助。

我不知道如何处理 sort()。我的 find() 有点工作，但是当我要求它找到一个值的节点时，它只返回我输入的值。

编辑： deleteAll() 现在可以正常工作了！

#include <iostream>
#include <limits>

using namespace std;

struct node
{
int data; //data
struct node *next; //link to next node
struct node *back; //link to previous node
};

class LinkedList //class LinkedList
{
struct node *root;
struct node *end;

int size;
public:

LinkedList() : root(NULL), size(0){}

bool isEmpty() const { return (root == NULL); }
void create();    //cleate list
void insert();    //insertion
void remove();    //deletion
void display();   //display list
void sort();     //sort list
void find();      //find a values' node
void deleteAll(); //delete all values
void retreive();  //retrive node
void getSize();      //return the number of nodes
};

//Creating a new list
void LinkedList::create()
{
struct node *nxt_node;
struct node *prev_node;

int value;
int n;
int i;

root = nxt_node = NULL;

cout << "How many nodes will the list have?: ";
cin >> n;

cout << "Enter the numbers to create the list: ";

for(i = 1; i <= n; i++)
{
    cin >> value;
    nxt_node = new node;
    nxt_node->data = value;
    nxt_node->next = NULL;
    nxt_node->back = NULL;

    if(root == NULL)
    {
        root = nxt_node;
    }
    else
    {
        prev_node->next = nxt_node;
        nxt_node->back = prev_node;
    }
    prev_node = nxt_node;
}
end = nxt_node;

size = n;

cout << endl;
cout << "The list has been created!" << endl;
cout << endl;
display();
}

//Displaying the list
void LinkedList::display()
{
if(isEmpty())
{
    cout << "The list is empty!" << endl;
    return;
}
else
{
    struct node *tmp = root;

    cout << "The list is: ";

    cout << "root -> ";
    while(tmp != NULL)
    {
        cout << tmp->data << " -> ";
        tmp = tmp->next;
    }
    cout << "end";
    cout << endl << endl;
}
}

//Instert a node anywhere
void LinkedList::insert()
{
int pos;
int dat;

struct node *ptr_b;
struct node *ptr_f;
struct node *tmp;

cout << "At what node do you want to insert the new data?: " << endl;
cout << "(If the node is not found the data will be added to the beginning)" << endl;
cout << "Node: ";
cin >> pos;

cout << endl;
cout << "Enter the data to be inserted: ";
cin >> dat;

ptr_b = root;
tmp = new node;
tmp->data = dat;

while(ptr_b->next != NULL && ptr_b->data != pos)
{
    ptr_b = ptr_b->next;
}
if(ptr_b->next == NULL && ptr_b->data != pos) //insertion to front
{
    root->back = tmp;
    tmp->next = root;
    tmp->back = NULL;
    root = tmp;
}
else if(ptr_b->next == NULL && ptr_b->data == pos) //insertion at the end
{
    ptr_b->next = tmp;
    tmp->next = NULL;
    tmp->back = ptr_b;
    end = tmp;
}
else // insertion between two nodes
{
    ptr_f = ptr_b->next;
    tmp->next = ptr_b->next;
    tmp->back = ptr_b;
    ptr_b->next = tmp;
    ptr_f->back = tmp;
}
size++;
cout << "The new data has been inserted!" << endl << endl;
display();
}

//remove any node
void LinkedList::remove()
{
int loc;
int dat;

struct node *ptr_b;
struct node *ptr_f;
struct node *tmp;

cout << "Enter the node to delete: ";
cin >> loc;

tmp = root;

if(loc < size && loc > 0) //return the value at loc
{
    int ind = 0;

    while(++ind < loc && tmp->next != NULL)
    {
        tmp = tmp->next;
    }
}
if(tmp->next == NULL && tmp->data != loc) //Data not found
{
    cout << "Node not found!" << endl << endl;
    return;
}
else if(tmp->next == NULL && tmp->data == loc) //Delete from the end of the list
{
    ptr_b = tmp->back;
    dat = tmp->data;
    ptr_b->next = NULL;
    end = ptr_b;
}
else //Delete between two nodes or first node
{
    dat = tmp->data;

    if(root == tmp) //delete the first node
    {
        root = tmp->next;
        ptr_f = root;
        ptr_f->back = NULL;
    }
    else //deletion between two nodes
    {
        dat = tmp->data;
        ptr_b = tmp->back;
        ptr_b->next = tmp->next;
        ptr_f = ptr_b->next;
        ptr_f->back = ptr_b;
    }
}
delete tmp;

size--;
cout << endl;
cout << "The node has been deleted!" << endl << endl;
display();
}

//retrieve a nodes data value
void LinkedList::retreive()
{
int loc;

//if the list is empty, say so
if(isEmpty())
{
    cout << "The List is empty!";
    return;
}
else
{
    //If the list is not empty
    cout << "What nodes' value do you want to retrieve?: ";
    cin >> loc;

    if(loc < size && loc > 0) //return the value at loc
    {
        struct node *tmp = root;

        int ind = 0;

        while(++ind < loc && tmp->next != NULL)
        {
            tmp = tmp->next;
        }
        cout << "The nodes value is: " << tmp->data << endl;
        cout << endl;
    }
    else //if the node is out of range
    {
        cout << "Invailid location!" << endl;
    }
}
}

//sort the list in acending order
void LinkedList::sort()
{
cout << "The list has been sorted!" << endl;
}

//delete all the values
void LinkedList::deleteAll()
{
struct node *tmp;

for(int i = 1; i < size; i++)
{
    while(root != NULL)
    {
        tmp = root;

        root = tmp->next;

        delete tmp;
    }
}
display();
}

//find a values' node
void LinkedList::find()
{
int value;

//if the list is empty, say so
if(isEmpty())
{
    cout << "The List is empty!";
    return;
}
else
{
    //If the list is not empty
    cout << "What values' node do you want to find?: ";
    cin >> value;

    struct node *tmp = root;

    int ind = 0;

    while(++ind < value && tmp->data != value)
    {
        tmp = tmp->next;
    }

    if(tmp->next == NULL && tmp->data != value) //Data not found
    {
        cout << "Value not found!" << endl << endl;
        return;
    }
    else
    {
        cout << "The value is at node: " << tmp->data << endl;
        cout << endl;
    }
}
}

void LinkedList::getSize()
{
cout << "The list has " << size << " nodes" << endl << endl;
}

int main()
{
LinkedList list;

list.create(); //create a new list
int choice;
while(1)
{
    cout << "What would you like to do? (1-7): " << endl;
    cout << "1. Insert a number" << endl;
    cout << "2. Delete a node" << endl;
    cout << "3. Delete ALL values" << endl;
    cout << "4. Retrieve a nodes' value" << endl;
    cout << "5. Retrives a values' node" << endl;
    cout << "6. Return the size of the list" << endl;
    cout << "7. Exit the program" << endl;
    cout << endl;

    cout << "Enter your choice (1-7): ";
    cin >> choice;
    cout << endl;

    switch(choice)
    {
        case 1: //insertion
            list.insert();
            break;
        case 2: //deletion
            list.remove();
            break;
       case 3: //delete all the values
            list.deleteAll();
            break;
        case 4: //retrieve a nodes' value
            list.retreive();
            break;
        case 5: //retrieve a values' node
            list.find();
            break;
        case 6: //returns the lists size
            list.getSize();
            break;
        case 7: //Exit the program
            exit(0);
            break;
        default:
            cout << "Please enter a vaild choice (1-7)!" << endl;
            break;
    }
}
return 0;
}

任何帮助，将不胜感激。我知道如果您不想在这两件事上都提供帮助，那么只需获得我即将完成的那一项（find()）就太棒了！

谢谢。

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1 回答 1

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对于 deleteAll，您的 for 循环需要从 0 开始，而不是从 1 开始（或转到 size+1）。考虑一个大小为 1 的列表，您的代码不会执行，这就是为什么在您的链表中剩下 1 个节点的原因。您的代码也需要重新考虑。而不是 for 循环可能是一个 while 循环？

struct node *tmp;
while (root != NULL)
{
    tmp = root;
    root = root->next;
    root->back = NULL;    //Is this even necessary? You're deleting ALL nodes.
    delete tmp;
}
display();

至于您的查找功能，您已将其设置为返回 void（无）。它正在打印节点值，因为您告诉它但您没有返回节点。您需要考虑 find 应该返回什么（节点或 null）。

我建议查找 QuickSort 对您的列表进行排序。因为这是一个特殊情况，您必须定制 QuickSort 以按节点-> 值排序，并且在排序时，您必须确保在交换值时节点指向正确的前一个和下一个节点。当您遇到更多错误时继续发布您的代码，并请确保您让我们知道您尝试了什么以及什么不起作用，我们很乐意帮助您指出正确的方向。

于 2011-11-01T01:47:10.410 回答