Postfix Evaluation Using Linked List Stack In Data Structure Using C++

on

Data Structure Using C++

Stack Data Structure

Postfix Evaluation Using Linked List Stack

class stack
{
 private:
  node *head;
 public:
  stack();
  void push(int val);
  int pop ();
  int top();
  int isEmpty ();
};
stack::stack()
{
 head=NULL;
}
void stack::push(int val)
{
 node *ptr= new node (val);
 ptr->setNext(head);
 head=ptr;
}
int stack::pop()
{
 if(isEmpty())
 {
  cout<<"Error: Stack is empty. can't pop element."<<endl;
 }
 else
 {
  int val=head->get();
  head=head->getNext();
  return val;
 }
}
int stack::top()
{
 return head->get();
}
int stack::isEmpty()
{
 return head==NULL;
}
int main ()
{
 stack s;
 char str[15]={'6','2','3','+','-','3','8','2','/','+','*','2','^','3' 
,'+'};
 int i=0;
 int op1, op2, result=0, ans=0;
 while(str[i]!='\0')
 {
  char ch=str[i];
  if(ch=='+'||ch=='-'||ch=='*'||ch=='/'||ch=='^')
  {
   op2=s.pop();
   op1=s.pop();
   cout<<op1<<" "<<op2<<endl;
   if(ch=='+')
   {
    result=op1+op2;
   }
   else if(ch=='-')
   {
    result=op1-op2;
   }
   else if(ch=='*')
   {
    result=op1*op2;
   }
   else if(ch=='/')
   {
    if(op2!=0)
    {
     result=op1/op2;
    }
   }
   else if(ch=='^'){
    result=pow(op1,op2);
   }
   cout<<endl<<result<<endl;
   s.push(result);
  }
  else
  {
   ch=ch-48;
   s.push(ch);
  }
  i++;
 }
 ans=s.pop();
 cout<<"Result is : "<<ans<<endl;
}

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