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Please Help me..........

qasim102 (1)
What is error in this code:
I have written this code for conversion of an Infix Expression into a Postfix expression using Stack,
please guide me in this....
thanks...
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  What is error in this:

#include "stdafx.h"

#include<iostream>
#include<string>
using namespace std;

class stack
{
private:
	int top;
	unsigned int size;
	char * data;
	string s,s1;
public:
	stack():top(-1){}
	stack(int n)
	{
		size=n;
		data=new char[n];
	}

	bool isEmpty()
	{
		if(top==-1)
			return true;
		else return false;
	}
	bool isFull()
	{
		if(top==size-1)
			return true;
		else return false;
	}
	void push(char element)
	{
		if(!isFull())
			cout<<"Stack is Full ";
		else
			data[++top]=element;
	}
	char pop()
	{
		if(isEmpty())
			cout<<"Stack is Empty";
		else return data[top--]; 
	}
	char topValue()
	{
		if(isEmpty())
			cout<<"Stack is empty";
		else return data[top];
	}
	void getinfix()
	{
		cout<<"Enter Your Infix Expression: ";
		cin>>s;
	}
	void showinfix()
	{
		cout<<s;
	}
	bool precedence()
	{
		for(int i=0;i<size-1;i++)
		if((s[i]=='+' && topValue()=='+')||(s[i]=='+' && topValue()=='-'))
		return true;
		else if((s[i]=='-' && topValue()=='-')||(s[i]=='-' && topValue()=='+'))
			return true;
		else if((s[i]=='*' && topValue()=='*')||(s[i]=='*' && topValue()=='/')||(s[i]=='*' && topValue()=='+')||(s[i]=='*' && topValue()=='-'))
		return true;
		else if((s[i]=='/' && topValue()=='/')||(s[i]=='/' && topValue()=='*')||(s[i]=='/' && topValue()=='+')||(s[i]=='/' && topValue()=='-'))
			return true;
		else return false;
	}
	void convert_Postfix()
	{
		stack(s.size());
		for(int i=0;i<size-1;i++)
		{
			if(s[i]>=97 && s[i]<=122)
			{
				s1+=s[i];
			}
			else if(s[i]=='(')
				push(s[i]);
			else if(!precedence())
				push(s[i]);
			else if(precedence())
			{
				s1+=pop();
				push(s[i]);
			}
			else if(s[i]==')')
				{
					while(!topValue()=='(')
						s1+=pop();
					pop();
				}
		}
		while(!isEmpty())
			s+=pop();
	}
	void showpostfix()
	{
		cout<<s1;
	}
	~stack()
	{
		delete[] data;
	}	
};
int main()
{
	stack s;
	s.getinfix();
	cout<<endl;
	s.showinfix();
	cout<<endl;
	s.convert_Postfix();
	s.showpostfix();
	system("pause");
	return 0;
}
Last edited on
fg109 (709)
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	stack(int n)
	{
		size=n;
		data=new char[n];
	}
//...
	void convert_Postfix()
	{
		stack(s.size());
//...
	}

You don't use constructor functions that way. You should change the function to void allocate(int n) or something.

Try adding s1 = ""; before the loop in convert_Postfix()

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			else if(precedence())
			{
				s1+=pop();
				push(s[i]);
			}

I'm not sure, but I think that should be

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			else if(precedence())
			{
				while(precedence())
					s1+=pop();
				push(s[i]);
			}


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	~stack()
	{
		delete[] data;
	}

Actually, since you only allocate the array inside convert_Postfix() and that's basically the only place where you deal with the array or call other functions that deal with the array, maybe you should have delete[] data; at the end of that function instead.

Also, why is line 66 there? for(int i=0;i<size-1;i++) You're only comparing with s[0] so why the need for a loop?

Maybe you should have all the functions private except for getinfix(), showinfix(), and showpostfix(), and have a function call to convert_Postfix() at the end of getinfix().
Last edited on
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