pop()函数是返回类型错误的函数。该函数表示它返回一个Stack对象,但数据在Node结构中。如何让它返回正确的数据?
根据我的显示功能,看起来没有数据进入堆栈。
添加newNode-> mData =数据并通过调试检查它看起来像堆栈中的东西。看来显示功能可能是问题。
我也不确定我的推送和isExist功能是否正确......
/* Pre: The stack is initialized and searchKey is available
* Post: The function retuns true if the searchKey exists in the queue;
* otherwise return false
* Purpose: To determine if a given value exists in the stack or not
*************************************************************************/
template <class T>
bool Stack<T>::isExist(T searchKey)
{
bool exist = false;
Node<T> *temp = mHead;
if (mHead == NULL)
{
exist = false;
}
else if (temp->mData == searchKey)
{
exist = true;
}
else
{
while (temp->mNext != NULL)
{
if (temp->mData == searchKey)
{
exist = true;
break;
}
temp = temp->mNext;
}
}
return exist;
}
/* Pre: The stack is initialized
* Post: The first node in the stack is removed, and its content is
* returned. If the stack is empty return the default value
* for the given data type
* Purpose: To remove the first node in the stack
*************************************************************************/
template <class T>
T Stack<T>::pop()
{
//Temp holds the mem location of the data
//that will be popped/returned
Node<T> *temp = mHead;
if (mHead == NULL)
{
return NULL;
cout << "The stack is empty!";
}
//Makes the next node in the stack the top one
else if (mHead->mNext == NULL )
{
mHead = NULL;
mTail = NULL;
}
else
{
mHead = mHead->mNext;
}
//Increment the counter down for the popped node
mCount--;
return temp->mData;
}
/* Pre: The stack is initialized
* Post: The new node is added at the beginning of the stack.
* Duplication is allowed
* Purpose: To add a new node at the beginning of the stack
*************************************************************************/
template <class T>
void Stack<T>::push(T data)
{
Node<T> *newNode = new Node<T>;
newNode->mData = data;
//If the stack is empty
if (mHead == NULL && mTail == NULL)
{
mHead = newNode;
mTail = newNode;
}
//Otherwise mHead will be the new node's next node
//The new node becomes the head
else
{
newNode->mNext = mHead;
mHead = newNode;
}
//Increment the counter to reflect the new node
mCount++;
}
template <class T>
void Stack<T>::display()
{
Node<T> *tmp;
if (isEmpty())
cout << "Empty Stack\n";
else
{
tmp = mHead;
while (tmp != NULL)
{
cout << tmp->mData << " ";
tmp = tmp->mNext;
}
cout << endl;
}
}
#ifndef STACK_H
#define STACK_H
#include <iostream>
using namespace std;
template <class T>
class Stack {
private:
template <class T>
struct Node
{
T mData;
Node<T> *mNext;
/* Pre: None
* Post: This object is initialized using default values
* Purpose: To intialize date object
*************************************************************************/
Node()
{
mData = T();
mNext = NULL;
}
/* Pre: None
* Post: This object is initialized using specified data
* Purpose: To intialize date object
*************************************************************************/
Node(T data)
{
mData = data;
mNext = NULL;
}
};
Node<T> *mHead, *mTail;
int mCount;
public:
Stack();
~Stack();
int getCount();
void clear();
void display();
bool isEmpty();
bool isExist(T searchKey);
T pop();
void push(T data);
};
template <class T>
Stack<T>::Stack()
{
mHead = NULL;
mTail = NULL;
mCount = 0;
}
template <class T>
Stack<T>::~Stack()
{
while (!isEmpty())
pop();
}
template <class T>
int Stack<T>::getCount()
{
return mCount;
}
template <class T>
void Stack<T>::clear()
{
while (!isEmpty())
pop();
}
template <class T>
void Stack<T>::display()
{
Node<T> *tmp;
if (isEmpty())
cout << "Empty Stack\n";
else
{
tmp = mHead;
while (tmp != NULL)
{
cout << tmp->mData << " ";
tmp = tmp->mNext;
}
cout << endl;
}
}
template <class T>
bool Stack<T>::isEmpty()
{
return mCount == 0;
}
#endif
答案 0 :(得分:1)
你错过了设置数据的步骤!
template <class T>
void Stack<T>::push(T data)
{
Node<T> *newNode = new Node<T>;
//HERE! vv
newNode->mData = data;
//THERE! ^^
//If the stack is empty
if (mCount == 0)
{
mHead = newNode;
mTail = newNode;
}
//Otherwise mHead will be the new node's next node
//The new node becomes the head
else
{
newNode->mNext = mHead;
mHead = newNode;
}
//Increment the counter to reflect the new node
mCount++;
}
(用户在编辑中修正了删除线文字)
需要考虑的其他事项:这个mTail
变量是什么,应该发生什么?
查看您的isExist
功能...问问自己,如果您推送一个号码然后询问该号码是否存在会发生什么?它会按预期工作吗?如果你尝试从空堆栈中弹出会发生什么?如果在空堆栈上调用isExist会发生什么?