CODEWITHSUNDEEP
c++ooppointersdata-structuresstack
pablomarti
pablomarti

Reputation: 2107

Problems while making a stack in C++ with auto referenced classes

I'm making a stack in C++ to manage infix, postfix and prefix mathematical operations. I use 2 classes, one called Node (an auto referenced class) and other one called Stack. In Node I have 2 properties, one is ID (an int, only for tests) and element (is a char*). In Stack I manage all the nodes in 2 stacks, one stack manages the operands (stack1) and another stack manages the operators (stack2). If I use the expression: "53+72-30/38*912", the idea is that in the stack2 for example I should have [ *, /, -, +] and the ids for each object [4, 3, 2, 1], but the result for stack2 is as follows [ *, *, *, *] but the ids for each one are fine [4, 3, 2, 1]

I think the problem must be with the char*, but I don't know how to solve it, can you help me please?

Thanks in advance!

Stack.cpp



//this is inside of a loop that goes trough a char* (named expr)
char tmp[i] = expr[i];
char op[] = {tmp, '\0'}; //I do this because the constructor of Node requieres a char*,
//and it is because I use the class Node to manage the stack of operands, which are char*
//for example, '983' (I do not use int for this case, but I also may create a template... 
//but I want to know how to make it with char*)
this->addOperatorToStack2(op);


Stack.cpp

//The method that adds an operator (a new node) to the stack
void Stack::addOperatorToStack2(char *op){
    Node *tmpNode = new Node(op);

    if(!currentNode){
        currentNode = tmpNode;
    }
    else{
        tmpNode->nextNode = currentNode;
        currentNode= tmpNode;
    }
}

Node.h

#ifndef NODE_H
#define NODE_H

class Node{

      friend class Stack;

      public:
              Node(char *);
              char* getElement() const;

      private:
              char *element;
              Node *nextNode;
              static int counter;
              int id;
};

#endif

Node.cpp

#include "Node.h"

Node::Node(char *element){
    this->nextNode = 0;
    this->element = element;

    counter++;
    id = counter;
}

char* Node::getElement()const{
    return this->element;
}

int Node::counter= 0;

Upvotes: 0

Views: 102

Answers (1)

c-smile
c-smile

Reputation: 27470

Each Node shall own its element value:

class Node{

      private:
              char element[MAXSIZE];
};

And so your constructor Node::Node(const char *element) shall make its own copy of the value - strncpy or some as such.

Upvotes: 1

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