Testing out my Reverse Polish stack...

closed account (S3TpfSEw)
Hi all. Just trying to get through this addition portion before moving on with the rest. Can't seem to figure out this pop,pop,push sequence. I know I'm heading in the right direction but can't nail down the exact coding. Any tips?

#include <iostream>


using namespace std;

class polishnode
{

public:

int numinput;
class polishnode *next;

polishnode(int operand, polishnode * ptr)
{
numinput = operand;
next = ptr;
}

};

class polishcalc
{

private:
polishnode *top;

public:
polishcalc()
{
top = 0;
}
bool isEmpty()
{
return top == 0;
}

int expressionentry(char * userinput)
{
int operand;

polishnode * temp;

char * pch;

pch = strtok (userinput, " ");
while(pch != NULL)
{
if (pch = "+")
{
int operandone;
int operandtwo;
int ans;


if (!isEmpty()) //pop first numerical value
operandone = top->numinput;
delete top;
top->next;

if (!isEmpty()) //pop second numerical value
operandtwo = top->numinput;
delete top;
top->next;

ans = operandone+operandtwo;

top->next = new polishnode(ans,top); //push answer back onto stack
}
else
top = new polishnode(operand,top); //push numerical value until an operator is read

}
return 0;

}

void print(char * userinput)
{
for(polishnode *temp = top; temp != 0; temp = temp->next)
{
cout<< " " << temp->numinput;
}
cout << endl;
}


};

int main ()
{
polishcalc input;
char userinput[99];
char * pch;
cout << "Please enter a reverse polish expression. \n";
cin.getline (userinput,99);

input.expressionentry(userinput);

input.print(userinput);

system("PAUSE");
}
TheJJJunk (181)
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#include <iostream>

using namespace std;

class polishnode
{

public: 

int numinput; 
class polishnode *next;

polishnode(int operand, polishnode * ptr)
{
numinput = operand;
next = ptr;
}

};

class polishcalc 
{

private: 
polishnode *top;

public: 
polishcalc()
{
top = 0;
}
bool isEmpty()
{
return top == 0;
}

int expressionentry(char * userinput)
{ 
int operand;

polishnode * temp;

char * pch;

pch = strtok (userinput, " ");
while(pch != NULL)
{
if (pch = "+")
{
int operandone;
int operandtwo;
int ans;


if (!isEmpty()) //pop first numerical value
operandone = top->numinput;
delete top;
top->next;

if (!isEmpty()) //pop second numerical value
operandtwo = top->numinput;
delete top;
top->next;

ans = operandone+operandtwo;

top->next = new polishnode(ans,top); //push answer back onto stack
}
else
top = new polishnode(operand,top); //push numerical value until an operator is read

}
return 0;

}

void print(char * userinput)
{
for(polishnode *temp = top; temp != 0; temp = temp->next)
{
cout<< " " << temp->numinput;
}
cout << endl;
}


};

int main ()
{ 
polishcalc input;
char userinput[99];
char * pch;
cout << "Please enter a reverse polish expression. \n";
cin.getline (userinput,99);

input.expressionentry(userinput);

input.print(userinput);

system("PAUSE");
}


It's the same code, just for easier reading
Last edited on
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