我已经通过valgrind和gdb运行了我的程序，每次我都得到一个分段错误核心转储错误，因为行T tempData = top ->数据;在我的Stack类中，但我不知道为什么。帮助！！！！
这是我的代码。第一个堆栈.h：
/*
* Stack.h
*
* Created on: Feb 4, 2014
* Author: csuser
*/
#ifndef STACK_H_
#define STACK_H_
#include <cstdlib>
#include <iostream>
#include "StackNode.h"
using namespace std;
template <class T>
class Stack
{
private:
StackNode<T> *top;
public:
Stack()
{
top = NULL;
}
void push(T c)
{
//allocate a stack node
StackNode<T> *stack1 = new StackNode<T>(c);
//make the top of the stack point to the new node, and if there was previously
//something in the stack, the old top's next node pointer points to the new top's
//pointer
stack1->next = top; //makes the new StackNode pointer point the old top of the stack
top = stack1; //makes the new StackNode pointer the top of the stack
}
T pop() //T because pop returns whatever T is
{
//saves the old top of the stack so when you reset top
//you don't lose the top of the stack
StackNode<T> *temp = top;
cout << "1 2 3" << endl;
***T tempData = top->data; ***
cout << "4 5 6" << endl;
top = top->next;
delete temp;
//returns the data from the StackNode that was popped
//i.e., allows you to see the operand
return tempData;
}
void printStack()
{
//Creates a pointer that points to the top of the stack
//So you can traverse through the stack by moving the pointer
StackNode<T> *ptr = top;
while (ptr != NULL)
{
cout << ptr->data << endl;
ptr = ptr->next; //Advances the pointer
}
}
StackNode<T>* getTop()
{
return top;
}
/*
T peek()
{
return top -> getData();
}
*/
};
#endif /* STACK_H_ */
/////////////This ends my first header file////////////////////////////
这是我的stacknode.h：
////////This begins my second and last header file////////////////
/*
* StackNode.h
*
* Created on: Feb 4, 2014
* Author: csuser
*/
#ifndef STACKNODE_H_
#define STACKNODE_H_
#include "Stack.h"
template <class T>
class Stack;
template <class T>
class StackNode
{
private:
T data;
StackNode<T> *next;
public:
friend class Stack<T>; //makes the Stack class a friend to the StackNode class
//StackNode Constructor function
StackNode(T Data)
{
data = Data;
next = NULL;
}
T getData()
{
return data;
}
StackNode* getNext()
{
return next;
}
};
#endif /* STACKNODE_H_ */
//////This ends my second and last header file///////
。和我的主要.cpp：
///////////This begins my main.cpp/////////////////////
/*
* Main.cpp
*
* Created on: Feb 4, 2014
* Author: csuser
*/
#include "Stack.h"
#include "StackNode.h"
#include <iostream>
#include <cstdlib>
#include <fstream>
#include <string>
using namespace std;
void convert(string, string);
double evaluate(string);
int precedence(char a);
int main()
{
//double answer;
string fileName;
cout << "Please enter a file name that has infix expressions" << endl;
cin >> fileName;
string infix;
ifstream infile;
infile.open(fileName.c_str());
if (infile.fail())
{
cout << "couldn't open text file..." << endl;
}
while (!infile.eof())
{
getline(infile, infix);
cout << "reading in the data..." << endl;
//cout << infix << endl;
string postFix(infix); //makes a string called postFix with the same length as infix
cout << "right before convert function call.." << endl;
convert(infix, postFix);
cout << "right after convert function call..." << endl;
//answer = evaluate(postFix);
//cout << answer << endl;
}
infile.close();
}
//Evaluate function
double evaluate(string postFix)
{
Stack<double> stk;
double left;
double right;
double result;
for (int i = 0; i<(int) postFix.length(); i++)
{
if (isdigit(postFix[i]))
{
stk.push(postFix[i]);
}
else if (postFix[i] == '*')
{
//pops one of the operands and puts it on the right hand side of a x + y operation
right = stk.pop();
//pops of of the operands and puts in on the left hand side of a x + y operation
left = stk.pop();
result = right * left;
stk.push(result);
}
else if (postFix[i] == '/')
{
//pops one of the operands and puts it on the right hand side of a x + y operation
right = stk.pop();
//pops of of the operands and puts in on the left hand side of a x + y operation
left = stk.pop();
result = left / right;
stk.push(result);
}
else if (postFix[i] == '+')
{
//pops one of the operands and puts it on the right hand side of a x + y operation
right = stk.pop();
//pops of of the operands and puts in on the left hand side of a x + y operation
left = stk.pop();
result = left + right;
stk.push(result);
}
else if (postFix[i] == '-')
{
//pops one of the operands and puts it on the right hand side of a x + y operation
right = stk.pop();
//pops one of the operands and puts in on the left hand side of a x + y operation
left = stk.pop();
result = left - right;
stk.push(result);
}
}
return stk.getTop()->getData();
}
//Convert function
void convert(string infix, string postFix)
{
Stack<char> stk;
char Data;
int j = 0;
char z;
//Use for loop to walk along the string
//the (int) in front of infix.length casts infix.length as an int
//because i is an int and string.length returns an unsigned int and we
//need the types to match
//cout << "Right before the for loop in convert function" << endl;
for (int i = 0; i<(int) infix.length(); i++)
{
//Case 1: an operand is found and is printed immediately
cout << "right before the first case in convert function" << endl;
if (isdigit(infix[i]))
{
//cout << "inside case one in convert" << endl;
postFix[j] = infix[i];
j++;
}
//cout << "right after case one in convert" << endl;
//Case 2: if a right parenthesis is found, then the stack is continuously popped
//until a left parenthesis is found
else if (infix[i] == ')')
{
//cout << "Inside case two in convert function" << endl;
while ((Data = stk.pop()) != '(')
{
//cout << "Data = " << Data << endl;
postFix[j] = Data;
j++;
}
}
//Case 3: if we see any other symbol besides a right parenthesis, excluding operands,
//we continuously pop the stack until we find an operator with lower precedence
else if ((infix[i] == '(') || (infix[i] == '*') || (infix[i] == '/') || (infix[i] == '+') || infix[i] == '-')
{
while (precedence(z = stk.pop()) >= precedence(infix[i]))
{
//Data = stk.pop();
stk.push(postFix[j] = z);
j++;
}
}
}
//prints out the rest of the stack
while (stk.getTop() != NULL)
{
postFix[j] = stk.pop();
j++;
}
}
//Precedence function
int precedence(char a)
{
if ((a == '(') || (a == ')'))
{
return 6;
}
else if ((a == '*') || (a == '/'))
{
return 5;
}
else if ((a == '-') || (a == '+'))
{
return 4;
}
else
{
return 0;
}
}
您正在取消引用null。您的堆栈是空的！不要问我为什么。改为调试我们的convert函数。
我没有仔细研究使用堆栈的代码，但您的 StackNode 和堆栈实现还可以（除了空堆栈处理）。