Question

我有一个任务：制作一个程序（C ++），它可以转换＆＃34; infix＆＃34;符号＆＃34;前缀＆＃34;并使用自己的＆＃34;堆栈和队列＆＃34;变现。

但我得到："Critical error detected c0000374"和"Free Heap block modified at ... after it was freed"最后一串void main() { /*...*/ system("pause"); }或最后一串void toPrefix();

有人可以帮我指出我的错误吗？

Source.cpp

#include "iostream"
#include "fstream"
#include "string"
#include "Stack.h"
#include "Queue.h"

void toPrefix(const std::string& first)
{
    int length = first.length();
    char test = NULL, operand = NULL;
    char *ptr = &test, *op_ptr = &operand;
    Queue<char> List;
    std::string Output;
    Stack<char> OpStack;
    for (int i = length - 1; i >= 0; i--) List.push(first[i]); //
    while (List.getsize() != 0)
    {
        List.pop(ptr);
        if (test >= 48 && test <= 57) //is it number?
        {
            Output.insert(Output.begin(), test);
        }
        if (test == '*' || test == '/' || test == '-' || test == '+')
        {
            OpStack.push(test);
        }
        if (test == ')')
        {
            OpStack.push(test);
        }
        if (test == '(')
        {
            OpStack.pop(op_ptr);
            while (operand != ')')
            {
                Output.insert(Output.begin(), operand);
                OpStack.pop(op_ptr);
            }
        }
    }
}

void main()
{
    const std::string& first = "9-(2+2)";
    toPrefix(first);
    system("pause");
}

Queue.h：

#include<iostream>

template <typename T>
class Queue
{
private:
    struct queue_element
    {
        T value;
        queue_element *next;
    };

    queue_element *first;
    queue_element *last;
    int size;

public:
    Queue()
    {
        first = new(queue_element);
        last = first;
        first->value = -1;
        first->next = 0;
        size = 0;
    }
    Queue(T x)
    {
        first = new(queue_element);
        last = first;
        first->value = x;
        first->next = 0;
        size = 1;
    }

    int getsize()
    {
        return size;
    }

    void push(T value)
    {
        if (size == 0)
        {
            size++;
            last = first;
            first->value = value;
            first->next = 0;
        }
        else
        {
            size++;
            queue_element *temp = new(queue_element);
            temp->next = 0;
            temp->value = value;
            last->next = temp;
            last = temp;
        }
    }

    void pop(T* ret)
    {
        if (size == 0)
        {
            std::cout << "Queue is empty!" << std::endl;
            return;
        }
        queue_element *temp = first;
        *ret = first->value;
        first = first->next;
        size--;
    }

    void peek(T *ret)
    {
        if (size == 0)
        {
            std::cout << "Queue is empty!" << std::endl;
            return;
        }
        *ret = first->value;
    }
};

Stack.h

#include <iostream>

template <typename T>
class Stack
{
private:
    struct stack_element
    {
        T value;
        stack_element *next;
    };
    stack_element *first;
    stack_element *last;
    int size;

public:
    Stack()
    {
        last = new(stack_element);
        first = last;
        last->value = -1;
        last->next = first;
        size = 0;
    }
    Stack(T x)
    {
        last = new(stack_element);
        first = last;
        last->value = x;
        last->next = 0;
        size = 1;
    }

    int getsize()
    {
        return size;
    }

    void push(T value)
    {
        if (size == 0)
        {
            size++;
            last->value = value;
            last->next = first;
        }
        else
        {
            size++;
            stack_element *temp = new(stack_element);
            temp->next = last;
            temp->value = value;
            last = temp;
        }
    }

    void pop(T* ret)
    {
        if (size == 0)
        {
            std::cout << "Stack is empty!" << std::endl;
            return;
        }
        stack_element *temp = last;
        *ret = last->value;
        last = last->next;
        delete temp;
        size--;
    }

    void peek(T *ret)
    {
        if (size == 0)
        {
            std::cout << "Stack is empty!" << std::endl;
            return;
        }
        *ret = first->value;
    }
};

Answer 1

嗯......我认为问题出在你身上Stack。

您传递给toPrefix()的字符串为"9-(2+2)"

因此Stack<char> OpStack中定义的toPrefix()中的操作是（如果我理解的话）

使用默认（无参数）构造函数构造
push()与-

pop()

(
push()与+
push()与)

好吧，让我们看看它里面发生了什么

1）构造后使用默认构造函数

我们有

1a）size == 0

1b）first，last，first->next和last->next指向相同的已分配内存区域

1c）first->value == last->value == (char)-1

2）第一次致电push()后（-）

我们有

2a）size == 1

2b）first，last，first->next和last->next指向相同的已分配内存区域

2c）first->value == last->value == '-'

3）第一次致电pop()

我们有

3a）size == 0

3b）指向同一DELETED内存区域的 first，last，first->next和last->next

3c）first->value == last->value == '-'

4）第二次呼叫push()（+}

4a）size递增

4b）在DELETED区域写入（last->value = value;）

4c）再次写入（last->next = first;）在DELETED区域

我想这可以解释你的问题。

p.s。：＆＃34;使用调试器＆＃34;来自Rambo Ramon和Sam Varshavchik的建议是一个很好的建议（恕我直言）

p.s.2：抱歉我的英语不好

将中缀转换为前缀表示法

1 个答案: