Program Plan - Define a char array exp[1000] for storing expression. Use an array buffer to read integer values larger than one digit. Add values to a stack defined as a vector of integers stack<int> s; To check if an entered character is an operator define a function bool isOperator ( char ch), which returns true or false. To perform postfix operation define one more function performOperation() which does post fix operation. Program Description - The objective of this program is to allow postfix operation to be performed if the operand is greater than 9. Program: //File: Stack.h //Template Stack Class Definition #ifndef STACK_H #define STACK_H #include<iostream> usingstd::cout; #include<new> #include "StackNode.h" template<typename T> class Stack { public: Stack(); ~Stack(); voidpush(T &); T pop(); boolisEmpty()const; T stackTop()const; voidprint()const; StackNode<T>*getTopPtr()const { returntopPtr; } private:StackNode<T>*topPtr; };//end class template stack //member function definitions template<typename T> Stack <T>:: Stack() { topPtr=0; } template<typename T> Stack <T>::~Stack() { StackNode<T>*tempPtr,*currentPtr=topPtr; while(currentPtr!=0) { tempPtr=currentPtr; currentPtr=currentPtr->getNextPtr(); deletetempPtr; }//end while }//end destructor //push node template<typename T> void Stack<T>::push (T &d) { StackNode<T>*newPtr=newStackNode<T>(d,topPtr); topPtr=newPtr; }//end function push //pop node template<typename T> T Stack<T>::pop() { StackNode<T>*tempPtr=topPtr; topPtr=topPtr->nextPtr; T poppedValue=tempPtr->data; deletetempPtr; returnpoppedValue; }//end function pop //is stack empty template<typename T> bool Stack<T>::isEmpty()const { returntopPtr==0; }//end function template<typename T> T Stack<T>::stackTop()const { return isEmpty()?getTopPtr()->getData():static_cast<T>(0); }//end function stackTop //display stack template<typename T> void Stack<T>::print()const { StackNode<T>*currentPtr=topPtr; if(isEmpty()) cout<<"Stack is empty"; else { cout<<"The stack is: \n"; while(currentPtr!=0) { cout<<currentPtr->data <<" "; currentPtr=currentPtr->nextPtr; }//end while cout<<"\n"; } } #endif //File:StackNode.h //Template StackNode Class definition #ifndef STACKNODE_H #define STACKNODE_H template<typename T>class Stack;//forward declaration template<typename T> classStackNode { friendclass Stack<T>; public: StackNode(const T &,StackNode*); T getData()const; //set point to next stack node voidsetNextPtr(StackNode*nPtr) { nextPtr=nPtr; }//end function StackNode*getNextPtr()const { returnnextPtr; } private: T data; StackNode*nextPtr; }; // Member function definitions template<typename T> StackNode<T>::StackNode(const T &d,StackNode<T>*ptr) { data=d; nextPtr=ptr; }//end constructor //get data template<typename T> T StackNode<T>::getData()const { return data; }//end function getData #endif #include<stdio.h> #include<iostream> #include<stdlib.h> #include"Stack.h" #include<string.h> usingnamespace std; boolisOperator(charch) { if(ch=='+'||ch=='-'||ch=='*'||ch=='/') returntrue; else returnfalse; } intperformOperation(int op1,int op2,char op) { intans; switch(op){ case'+': ans= op2 + op1; break; case'-': ans= op2 - op1; break; case'*': ans= op2 * op1; break; case'/': ans= op2 / op1; break; } returnans; } intmain() { charexp[1000], buffer[15]; inti,op1, op2,len, j, x; Stack<int> s; printf("Enter a Postfix Expression: ( e.g. 17 4 * 4 + )\n"); gets(exp); len=strlen(exp); j =0; for(i=0;i<len;i++){ if(exp[i]>='0'&& exp[i]<='9'){ buffer[j++]= exp[i]; } elseif(exp[i]==' '){ if(j>0){ buffer[j]='\0'; x =atoi(buffer); s.push(x); j =0; } } elseif(isOperator(exp[i])){ op1 =s.pop(); //s.pop(); op2 =s.pop(); //s.pop(); intpushValue=performOperation(op1, op2, exp[i]); s.push(pushValue); } } printf("Answer is %d\n"); s.print(); return0; } Sample Output: Enter a Postfix Expression: ( e.g. 17 4 * 4 + ) 17 4 * 4 + The stack is: 72

Solution Summary: The author explains the purpose of the program, which is to allow postfix operation to be performed if the operand is greater than 9.

Chapter 19 Solutions