我制作了一个基本程序，用于为中间C ++类创建一个整数堆栈。整个事情编译得很好，但是我遇到了2个问题：容量总是显示为0，当我测试重载的赋值运算符（Stack1 = Stack2）时会出现段错误。我知道这可能是因为同样的事情，但应该改变什么呢？
#include <iostream>
#include <ostream>
#include <cstring>
#include <stdexcept>
using namespace std;
class Stack
{
//overloaded "<<" for outputting the stack's contents
friend ostream& operator<<(ostream& leftOp, const Stack& rightOp);
public:
Stack(); //constructor
Stack(const Stack& s); //copy constructor
~Stack(); //destructor
const Stack& operator=(const Stack& rightOp); //assign one stack to another
void clear(); //set the stack size back to 0
bool empty() const; //checks whether or not the stack is empty
unsigned int size() const; //returns the size
unsigned int capacity() const; //returns the capacity
int top() const throw(out_of_range); //returns the top value
void push(int item); //adds a new value
void pop() throw(out_of_range); //removes the top value
void reserve(unsigned int newCapacity); //enlarges the array
private:
unsigned int stackCap; //stack capacity
unsigned int stackSize; //stack size
int* stackArray; //pointer to the stack, to be dynamically allocated
};
int main()
{
cout << "Testing default constructor\n\n";
Stack s1;
cout << "s1: " << s1 << endl;
cout << "s1 size: " << s1.size() << ", capacity: " << s1.capacity() << endl;
cout << "s1 is " << ((s1.empty()) ? "empty\n" : "not empty\n");
cout << endl;
cout << "Testing push()\n\n";
for (int i = 10; i < 80; i+= 10)
s1.push(i);
cout << "s1: " << s1 << endl;
cout << "s1 size: " << s1.size() << ", capacity: " << s1.capacity() << endl;
cout << "s1 is " << ((s1.empty()) ? "empty\n" : "not empty\n");
cout << endl;
for (int i = 15; i < 85; i+= 10)
s1.push(i);
cout << "s1: " << s1 << endl;
cout << "s1 size: " << s1.size() << ", capacity: " << s1.capacity() << endl;
cout << "s1 is " << ((s1.empty()) ? "empty\n" : "not empty\n");
cout << endl;
cout << "Testing copy constructor()\n\n";
Stack s2 = s1;
cout << "s1: " << s1 << endl;
cout << "s1 size: " << s1.size() << ", capacity: " << s1.capacity() << endl;
cout << "s1 is " << ((s1.empty()) ? "empty\n" : "not empty\n");
cout << endl;
cout << "Testing top()\n\n";
cout << "Top item of s1: " << s1.top() << endl << endl;
cout << "Testing pop()\n\nTop item of s1: ";
while (!s1.empty())
{
cout << s1.top() << ' ';
s1.pop();
}
cout << endl << endl;
cout << "s1: " << s1 << endl;
cout << "s1 size: " << s1.size() << ", capacity: " << s1.capacity() << endl;
cout << "s1 is " << ((s1.empty()) ? "empty\n" : "not empty\n");
cout << endl;
cout << "Testing assignment operator\n\n";
Stack s3;
s3 = s2;
cout << "s2 (size " << s2.size() << "): " << s2 << endl;
cout << "s3 (size " << s3.size() << "): " << s3 << endl << endl;
cout << "Testing clear()\n\n";
s2.clear();
cout << "s2: " << s2 << endl;
cout << "s2 size: " << s2.size() << ", capacity: " << s2.capacity() << endl;
cout << "s2 is " << ((s2.empty()) ? "empty\n" : "not empty\n");
cout << endl;
cout << "s3: " << s3 << endl;
cout << "s3 size: " << s3.size() << ", capacity: " << s3.capacity() << endl;
cout << "s3 is " << ((s3.empty()) ? "empty\n" : "not empty\n");
cout << endl;
cout << "Testing assignment to self and swap\n\n";
s3 = s3;
s2 = s3;
s3.clear();
cout << "s2 (size " << s2.size() << "): " << s2 << endl;
cout << "s3 (size " << s3.size() << "): " << s3 << endl << endl;
cout << "Testing chained assignment\n\n";
Stack s4;
s4 = s3 = s2;
cout << "s2 (size " << s2.size() << "): " << s2 << endl;
cout << "s3 (size " << s3.size() << "): " << s3 << endl;
cout << "s4 (size " << s4.size() << "): " << s4 << endl << endl;
cout << "Testing const correctness\n\n";
const Stack& r4 = s4;
cout << "s4: " << r4 << endl;
cout << "s4 size: " << r4.size() << ", capacity: " << r4.capacity() << endl;
cout << "s4 is " << ((r4.empty()) ? "empty\n" : "not empty\n");
cout << "\nTop item of s4: " << r4.top() << endl << endl;
s1 = r4;
cout << "s1: " << s1 << endl;
cout << "s1 size: " << s1.size() << ", capacity: " << s1.capacity() << endl;
cout << "s1 is " << ((s1.empty()) ? "empty\n" : "not empty\n");
cout << endl;
s1.clear();
cout << "s1: " << s1 << endl;
cout << "s1 size: " << s1.size() << ", capacity: " << s1.capacity() << endl;
cout << "s1 is " << ((s1.empty()) ? "empty\n" : "not empty\n");
cout << endl;
cout << "Testing top() with empty stack\n\n";
try
{
cout << s1.top() << endl;
}
catch (out_of_range orex)
{
cout << orex.what() << endl << endl;
}
cout << "Testing pop() with empty stack\n\n";
try
{
s1.pop();
}
catch (out_of_range orex)
{
cout << orex.what() << endl;
}
return 0;
}
Stack::Stack()
{
stackCap = 0;
stackSize = 0;
stackArray = '\0';
}
Stack::Stack(const Stack& s) //copy constructor
{
stackCap = s.capacity();
stackSize = s.size();
if (s.stackCap == 0)
stackArray = '\0';
else
{
stackArray = new int[stackCap];
for (unsigned int i=0; i < stackSize; i++) //copy the string except for the nullbyte
{
stackArray[i] = s.stackArray[i]; //copy it one character at a time into the main string
}
}
}
Stack::~Stack() //destructor
{
delete stackArray;
}
const Stack& Stack::operator=(const Stack& rightOp) //assign one stack to another
{
if (rightOp.stackArray == '\0')
{
stackCap = 0;
stackSize = 0;
stackArray = '\0';
}
else
{
delete[] stackArray; //delete that array that is the wrong size!
stackSize = rightOp.stackSize;
stackCap = rightOp.stackCap;
if (rightOp.capacity() == 0)
stackArray = '\0';
else
{
stackArray = new int[stackCap];
for (unsigned int i=0; i < stackSize; i++) //copy the string except for the nullbyte
{
stackArray[i] = rightOp.stackArray[i]; //copy it one character at a time into the main string
}
}
}
return *this;
}
void Stack::clear()
{
stackSize = 0;
}
bool Stack::empty() const
{
return (stackSize == 0);
}
unsigned int Stack::size() const
{
return stackSize;
}
unsigned int Stack::capacity() const
{
return stackCap;
}
int Stack::top() const throw(out_of_range)
{
if ( empty() == true )
throw out_of_range("top(): stack is empty");
else
return stackArray[stackSize];
}
void Stack::push(int item)
{
if (stackCap == stackSize)
reserve(stackCap * 2);
stackArray[stackSize] = item;
stackSize++;
}
void Stack::pop() throw(out_of_range)
{
if ( empty() == true )
throw out_of_range("top(): stack is empty");
stackSize--;
if (stackSize > 0 && stackSize == stackCap / 4)
reserve(stackCap / 2);
}
void Stack::reserve(unsigned int newCapacity)
{
int* copyArray = new int[newCapacity];
for (unsigned int i = 0; i < stackSize; i++)
{
copyArray[i] = stackArray[i];
}
stackCap = newCapacity;
delete[] stackArray;
stackArray = copyArray;
}
ostream& operator<<(ostream& leftOp, const Stack& rightOp) //prints out the stacks contents
{
for (unsigned int i = 0; i < rightOp.stackSize; i++) //run the loop for the number of rightOp elements
leftOp << rightOp.stackArray[i] << " "; //read the elements into leftOp stream
return leftOp;
}
答案 0 :(得分：1)
您的代码没有很好地处理s3 = s3;。您删除后引用了s3.stackArray。
解决此问题的一种方法是在if (this == &rightOp) return *this;的开头添加operator=()。
此外，由于您的初始容量为0，并且您总是按reserve(stackCap * 2)增长，因此它始终保持为0.要么使用非0初始容量，要么专门处理0。