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Question

我想創建一個函數，將insert a node to the back of the list using linked list。我是新來的使用鏈表，我已經嘗試了許多不同的方式在列表的末尾做插入，但似乎沒有任何工作。 main傳遞值one at a time以插入2 4 5 8 9，輸出爲2 0 0 0 0。我不是什麼導致這個問題。

.H

class Node 
{ 
public: 
    Node() : data(0), ptrToNext(NULL) {} 
    Node(int theData, Node *newPtrToNext) : data(theData), ptrToNext(newPtrToNext){} 
    Node* getPtrToNext() const { return ptrToNext; } 
    int getData() const { return data; } 
    void setData(int theData) { data = theData; } 
    void setPtrToNext(Node *newPtrToNext) { ptrToNext = newPtrToNext; } 
    ~Node(){} 
private: 
    int data; 
    Node *ptrToNext; //pointer that points to next node 
}; 

class AnyList 
{ 
public: 
    AnyList(); 
     //default constructor 
    void print() const; 
     //Prints all values in the list. 
    void destroyList(); 
     //Destroys all nodes in the list. 
    ~AnyList(); 
     //destructor 
    int getNumOfItems(); 
    void insertBack(int b); 
    void deleteFirstNode(); 

private: 
    Node *ptrToFirst; //pointer to point to the first node in the list 
    int count;  //keeps track of number of nodes in the list 
}; 

的.cpp

void AnyList::insertBack(int b) 
{ 
    Node *temp = new Node; 

    if (ptrToFirst == NULL) 
    { 
     temp->setData(b); 
     ptrToFirst = temp; 
    } 
    else 
    { 
     Node *first = ptrToFirst; 
     while (first->getPtrToNext() != NULL) 
     { 
      first = first->getPtrToNext(); 
     } 
     first->setPtrToNext(temp); 
    } 
} 

Answer 1

首先，你真的應該使用std::list或std::forward_list類，而不是執行節點手動處理：

#include <list> 

class AnyList 
{ 
public: 
    void print() const; 
     //Prints all values in the list. 
    void destroyList(); 
     //Destroys all nodes in the list. 
    int getNumOfItems() const; 
    void insertBack(int b); 
    void deleteFirstNode(); 

private: 
    std::list<int> nodes; //nodes in the list 
}; 

void AnyList::print() const 
{ 
    for (std::list<int>::const_iterator iter = nodes.begin(); iter != nodes.end(); ++iter) 
    { 
     int value = *iter; 
     // print value as needed... 
    } 
} 

void AnyList::destroyList() 
{ 
    nodes.clear(); 
} 

void AnyList::getNumOfItems() const 
{ 
    return nodes.size(); 
} 

void AnyList::insertBack(int b) 
{ 
    nodes.push_back(b); 
} 

void AnyList::deleteFirstNode() 
{ 
    if (!nodes.empty()) 
     nodes.pop_front(); 
} 

話雖這麼說，你的手工執行失敗，因爲你很可能沒有正確管理節點（但你沒有告訴你正在做的一切）。它應該是這個樣子：

class Node 
{ 
public: 
    Node() : data(0), ptrToNext(NULL) {} 
    Node(int theData, Node *newPtrToNext) : data(theData), ptrToNext(newPtrToNext) {} 
    ~Node() {} 
    Node* getPtrToNext() const { return ptrToNext; } 
    int getData() const { return data; } 
    void setData(int theData) { data = theData; } 
    void setPtrToNext(Node *newPtrToNext) { ptrToNext = newPtrToNext; } 
private: 
    int data; 
    Node *ptrToNext; //pointer that points to next node 
}; 

class AnyList 
{ 
public: 
    AnyList(); 
     //default constructor 
    ~AnyList(); 
     //destructor 
    void print() const; 
     //Prints all values in the list. 
    void destroyList(); 
     //Destroys all nodes in the list. 
    int getNumOfItems() const; 
    void insertBack(int b); 
    void deleteFirstNode(); 

private: 
    Node *ptrToFirst; //pointer to point to the first node in the list 
    Node *ptrToLast; //pointer to point to the last node in the list 
    int count;  //keeps track of number of nodes in the list 
}; 

AnyList:AnyList() 
    : ptrToFirst(NULL), ptrToLast(NULL), count(0) 
{ 
} 

void AnyList::print() const 
{ 
    for (Node *temp = ptrToFirst; temp != NULL; temp = temp->getPtrToNext()) 
    { 
     int value = temp->getData(); 
     // print value as needed... 
    } 
} 

AnyList::~AnyList() 
{ 
    destroyList(); 
} 

void AnyList::destroyList() 
{ 
    Node *temp = ptrToFirst; 
    ptrToFirst = ptrToLast = NULL; 
    count = 0; 

    while (temp != NULL) 
    { 
     Node *next = temp->getPtrToNext(); 
     delete temp; 
     temp = next; 
    } 
} 

int AnyList::getNumOfItems() const 
{ 
    return count; 
} 

void AnyList::insertBack(int b) 
{ 
    Node *temp = new Node(b, NULL); 

    if (ptrToFirst == NULL) 
     ptrToFirst = temp; 

    if (ptrToLast != NULL) 
     ptrToLast->setPtrToNext(temp); 

    ptrToLast = temp; 
    ++count; 
} 

void AnyList::deleteFirstNode() 
{ 
    if (ptrToFirst == NULL) 
     return; 

    Node *temp = ptrToFirst; 
    ptrToFirst = temp->getPtrToNext(); 

    if (ptrToLast == temp) 
     ptrToLast = NULL; 

    delete temp; 
    --count; 
}