c++ - 调用堆栈打印功能时的无限循环

该程序应采用后缀算术表达式，然后编译该表达式的值。每次读取一个整数时，它将被压入堆栈。否则，如果读取+，-，*，则将弹出两个整数。

class Stack {
    Node *head;

public:
    Stack() {
        head = NULL;
    };

    void push(int data);
    int pop();
    bool isEmpty();
    void print();
};

void Stack::push(int data)
{
    Node * temp = new Node(data);
    temp->next = head;
    head = temp;
    delete temp;
}

int Stack::pop()
{
    int x = head->data;
    head = head->next;
    return x;
}

bool Stack::isEmpty(){
    return head == NULL;
}

void Stack::print(){
    Node * temp = head;
    while (temp != NULL){
        cout << temp->data << " ";
        temp = temp->next;
    }
    delete temp;
}


int main() {

    Stack st;
    char exp [] = "23+", c;
    int i, a;

    for (i = 0; exp[i] != '\0'; i++){
        c = exp[i];

        if (c == '+'&&!st.isEmpty()){
            a = st.pop() + st.pop();
            st.push(a);
        }
        else if (c == '-'&&!st.isEmpty()){
            a = st.pop() - st.pop();
            st.push(a);
        }
        else if (c == '/'&&!st.isEmpty()){
            a = st.pop() / st.pop();
            st.push(a);
        }
        else if (c == '*'&&!st.isEmpty()){
            a = st.pop() * st.pop();
            st.push(a);
        }
        else if (c == '0')
            st.push(0);
        else if (c == '1')
            st.push(1);
        else if (c == '2')
            st.push(2);
        else if (c == '3')
            st.push(3);
        else if (c == '4')
            st.push(4);
        else if (c == '5')
            st.push(5);
        else if (c == '6')
            st.push(6);
        else if (c == '7')
            st.push(7);
        else if (c == '8')
            st.push(8);
        else if (c == '9')
            st.push(9);

        cout << c << endl;
        st.print();
    }
    cin >> a;
    return 0;
}

当我在main中调用print函数时，我得到一个无限循环作为输出。
我试图寻找导致无限循环的事物，但我找不到它。

最佳答案

我看到的问题:

在delete中使用push():

void Stack::push(int data)
{
    Node * temp = new Node(data);
    temp->next = head;
    head = temp;
    delete temp;  // This needs to go.
}

在delete中不使用pop():

int Stack::pop()
{
    // Problem 1.
    // What if head is NULL?

    int x = head->data;

    // Problem 2
    // The old value of head is gone. It's a memory leak.
    head = head->next;
    return x;
}

你需要:

int Stack::pop()
{
   if ( head != NULL )
   {
      int x = head->data;
      Node * temp = head;
      head = head->next;
      delete temp;
      return x;
   }
   else
   {
      // Figure out what you want to do if head is NULL
   }
}

在delete中使用print()。

void Stack::print(){
    Node * temp = head;
    while (temp != NULL){
        cout << temp->data << " ";
        temp = temp->next;
    }
    delete temp; // This needs to go.
}

缺少用户定义的析构函数。您需要删除对象中的对象。否则，您正在泄漏内存。遵循以下代码的代码应该可以工作。

Stack::~Stack()
{
   while (head)
   {
      Node * temp = head;
      head = head->next;
      delete temp;
   }
}

关于c++ - 调用堆栈打印功能时的无限循环，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/28684263/