Question

我正在尝试将中缀转换为posfix，但优先级不起作用。请帮忙！代码是用C ++编写的。我的代码打印出“ABCDEF + ** + *”，当我认为它应该打印出“ABCDEF **** ++”，如果我正确理解这一点。 *优先于+。感谢你们对我的帮助。这是我的代码：

#include <iostream>
#include <string>
using std::cout;
using std::cin;
using std::endl;
using std::string;

struct node{
    char value;
    struct node *link;
};

node *top;

class stack{
private:
    int counter;
public:
    node *pushInto(node*, char);
    node *popOut(node*);
    void traverseStack(node*);
    int isStackEmpty();
    stack()
    {
        top = nullptr;
        counter = 0;
    }
};

node *stack::pushInto(node *top, char a)
{
    node *temp;
    temp = new (struct node);
    temp -> value = a;
    temp -> link = top;
    top = temp;
    counter++;
    return top;
}

node *stack::popOut(node *top)
{
    node *temp;
    char item;
    if (top == nullptr)
    {
        cout << "Stack is empty";
    }
    else
    {
        temp = top;
        item = temp -> value;
        cout << item;
        top = top -> link;
        delete temp;
        counter--;
    }
    return top;
}

void stack::traverseStack(node *top)
{
    node *temp;
    temp = top;
    if (top == nullptr)
    {
        cout << "Stack is empty.";
    }
    else
    {
        while (temp != nullptr)
        {
            cout << temp -> value << endl;
            temp = temp -> link;
        }
    }
}

int stack::isStackEmpty()
{
    if (top == nullptr)
        return 0;
    return -1;
}

class infixToPostfix:public stack{
public:
    bool isOperand(char);
    bool isOperator(char);
    int weightOfOperator(char);
    char precedence(char, char);
    void output(char[]);
};

bool infixToPostfix::isOperand(char a)
{
    if (a >= 'A' && a <= 'Z')
        return true;
    return false;
}

bool infixToPostfix::isOperator(char a)
{
    if (a == '*' || a == '/' || a == '+' || a == '-')
        return true;
    return false;
}

int infixToPostfix::weightOfOperator(char a)
{
    int weight;

    if (a == '*' || a == '/')
        weight = 2;
    else if (a == '+' || a == '-')
        weight = 1;
    else
        weight = -1;
    return weight;
}

char infixToPostfix::precedence(char a, char b)
{
    if (weightOfOperator(a) > weightOfOperator(b))
    {
        return a;
        return b;
    }
    return NULL;
}

void infixToPostfix::output(char a[])
{
    const int length = 11;
//    const int numberOperators = 5;
    char output[length];
    for (int i = 0; i < length; i++)
    {
        if (isOperand(a[i]))
        {
            output[i] = a[i];
        }
        else
        {
            top = pushInto(top, a[i]);
        }
        cout << output[i];
    }

    for (int i = 1; i < length; i+=2)
    {
        if (precedence(a[i], a[i + 1]))
        {
            top = popOut(top);
        }
    }
}

int main()
{
    infixToPostfix result;
    const int length = 11;
    char infix1[length] = {'A', '*', 'B', '+', 'C', '*', 'D', '*', 'E', '+', 'F'};  //Initalize and declare first infix pattern
  //  char infix2[length] = {'A', '+', 'B', '*', 'C', '+', 'D', '+', 'E', '*', 'F'};

    result.output(infix1);
    cout << "\n";
//    result.output(infix2);

    return 0;
}

Answer 1

A*B+C*D*E+f is AB*CD*E*+F+

的后缀

您的优先功能似乎不正确

char infixToPostfix::precedence(char a, char b)
{
    if (weightOfOperator(a) > weightOfOperator(b))
    {
        return a;
        return b;// unreachable
    }
    return NULL // return type does not match
}

将其更改为

char infixToPostfix::precedence(char a, char b)
{
    if (weightOfOperator(a) > weightOfOperator(b))
    {
        return a;

    }
    return b;
}

中缀到后缀 - 优先级不起作用

1 个答案: