Chapter 9 – Stack NCERT Solutions for Class 12 Computer Science (C++)

NCERT Solutions for Class 12 Computer Science (C++) Chapter 9 – Stack – Free PDF download

NCERT Solutions for Class 12 Computer Science

Short Answer Type Questions-I[2 marks each]

Question 1.
Evaluate the following postfix expression. Show the status of stack after execution of each operation separately:
2,13, + , 5, -,6,3,/,5,*,<
Answer:

RESULT = FALSE

Question 2.
Evaluate the following postfix expression : (show status of Stack after each operation)
100,40,8,/,20,10,-,+,*
Answer:

Question 3.
Evaluate the following postfix expression. Show the status of stack after execution of each operation separately:
T, F, NOT, AND, T, OR, F, AND
Answer:

Thus the stack will have False Value

Question 4.
Evaluate the following postfix expression. Show the status of stack after execution of each operation separately:
F, T, NOT, AND, F, OR, T, AND
Answer:

Thus the stack will have False Value

Question 5.
Evaluate the following postfix expression using a stack and show the contents of stack after execution of each operation:
5,3,2, *, 4,2, /, -,*
Answer:

Result=20

Question 6.
Evaluate the following POSTFIX notation. Show status of Stack after every step of evaluation (i.e. after each operation)
False NOT, True, AND, True, False, OR, AND
Answer:

Final Answer: True

Question 7.
Top is a pointer variable pointing to the top element of a stack, with each node having the following structure declaration:
struct Stack {int Data, Stack * Next};
Considering the above explanation, what will the following code do ?
int count = 0, Sum = 0;

Stack * Temp = Top;  while (Temp - > Next! = NULL)  { count + +;  Sum + = Temp - > Data;  Temp Temp - > Next;  }  count < < Sum / count;

Answer:
It will calculate the average of stack values.

Question 8.
Convert the expression ((x * 3 + y * 3 + z * 3) / (x + y + z)) into postfix expression. Show the content of the stack during the conversion.
Answer:
Given expression : ((x * 3 + y * 3 + z * 3) / (x + y + z))
((x * 3 + y * 3 + z * 3) / (x + y + z))

Postfix expression is: x3y3z3 * + * + * xyz + +/

Question 9.
Evaluate the following POSTFIX expression, show the status of Stack after execution of each operation separaterly:
45,45,+,32,20,10,/,-,*
Answer:

Hence the final result is 2700

Question 10.
Convert the following Infix expression to its equivalent Postfix expression, showing the stack contents for each step of conversion.
P/Q+(R-T)*U
Answer:
P/Q+(R-T)*U = (P/Q+(R-T)*U)

Short Answer Type Questions-II[3 marks each]

Question 1.
Write the definition of a member function Pop ()
in C++, to delete a book from a dynamic stack of TEXTBOOKS considering the following code is already included in the program.

Struct TEXTBOOKS  {  Char ISBN [20]; Char TITLE [80]; TEXTBOOKS *Link;  };  class STACK  {  TEXTBOOKS *Top;   public :  STACK () {Top = NULL;}   void Push ();  . void pop );  -STACK ();  };

Answer:

void STACK : : POP ()  {  if (Top ! = NULL) {  TEXTBOOKS *Temp;  Temp=Top; cout<< TOP- >ISBN<<Top-  TITLE<<"delected"<<endl;  Top=Top-Link;  delete Temp;  }  else  cout<<"Stack Empty"<<endl;  }

OR
Any other correct equivalent function definition

Question 2.
Write the defintion of a member function PUSH () in C+ +, to add a new book in a dynamic stack of BOOKS considering the following code is already included in the program :

struct BOOKS  {  Char ISBN [20]; TITLE[80];  BOOKS *Link;  };  class STACK  {  BOOKS *Top;  public :  STACK () {Top = NULL;}  void PUSH ();  Void POP ();  -STACK ();  };

Answer:

void STACK :: PUSH ()  {  BOOKS *Temp;  Temp=New BOOKS;  gets (Temp->ISBN);  gets (Temp->TITLE);  Temp->Link =Top;  Top=Temp;  }

OR
Any other correct equivalent function definition

Question 3.
Convert the expression (A-5)*6+(10/B)/2 to corresponding postfix expression. Also show the status of operator stack after each step.
Answer:
((A-5)*6+(10/B)/2)

The correspondence postfix expression is A, 5, 6, 10, B, /,2, /,+

Long Answer Type Questions[4 marks each]

Question 1.
Convert the following Infix expression to its equivalent Postfix expression, showing the stack contents for each step of conversion.
A/(B+C)*D-E
Answer:
A/ (B + C) *D-E

Question 2.
Write definition for a function DISPMID (int A[][5], int R, int C) in C+ + to display the elements of middle row
and middle column from a two dimensional array A having R number of rows and C number of columns.
For example, if the content of array is as follows:

The function should display the following as output:
103 901 921 802
601 516 921 609
Answer:

void DISPMID (int A[] [5] , int R, int C)  {  int mid = (R+C)/2;  for (int i=0; i<c; i++)  {  Cout << A[mid] [i]<<"";  } cout<<endl;  for (int i=0; i<R; i++)  cout << A[i][mid]<<"";  }

Question 3.
Convert the following Infix expression to its equivalent Postfix expression, showing the stack contents for each step of conversion.
P/(Q-R)*S+T
Answer:
P/(Q-R)*S+T
BODMAS : PQR-/S*T+
PQR-/S*T+

Question 4.
Convert the following infix expression to its equivalent postfix expression, showing the stack contents for each step of conversion:
X/Y+U*(V-W)
Answer:
X / Y + U* (V – W) = ((X / Y) + (U * (V – W)))

OR

OR

Any other method or converting the given Infix expression to its equivalent Postfix expression showing stack contents

Question 5.
Evaluate the following postfix expression using stack and show the contents after excecution of each.
Answer:
Operations : 470,5,4,∧,25,/,6,*

Question 6.
Write member functions to perform POP and PUSH operations in a dynamically allocated stack containing the objects of the following structure:

struct Game  { char Gamename[30];  int numofplayer;  Game *next; } ;

Answer:

struct Game  {  char Gamename[3 0] ;  int numofplayer;  Game *next;  };  class Stack { Game *Top;  public :  Stack ()  {  Top = NULL;  }  void Push();  void Pop();  void display();  -Stack();  } ;  void Stack::Push()  {  Game *temp = new Game;  cout<<"Enter Data : "; gets(temp->Gamename);  cin>>temp->numofplayer;  temp->next =Top;  Top = temp;  }  void Stack:: Pop()  {  if ( Top != NULL)  {  Game *temp = Top;  cout<Gamename<<" Deleted"; Top = Top->next;  delete temp;  }  else  cout<<"Stack is empty....";  }

Question 7.
Write a function PUSHBOOK() in C++ to perform insert operation on Dynamic Stack, which contains Book_no and Book_Title. Consider the following definition of NODE, while writing your C+ + code,

struct NODE { int Book_No ; char Book_Title [20]; NODE * Next; };

Answer:

Void PUSHBOOK (NODE *TOP> int Book_No, char B Title [20])  {  NODE*temp;  temp=new NODE;  temp —> Book_No=Book_No;  Strcpy (temp —> Book_Title, B Title) ;  temp --> Next=NULL ;  if (Top==NULL)  Top=temp;  else  {  temp —> Next=top;  Top==temp;  }  }

Question 8.
Write a function POPBOOK( ) in C++ to perform delete operation from a Dynamic Stack, which contains Bno and Title. Consider the following definition of NODE, while writing your C++code.

struct NODE { int Bno; char Title[20] ; NODE * Link; } ;

Answer:

node*PopBOOK(node*TOP int Bno, char B Title [20]) { node*temp; temp=new node; temp —>Bno=Bno; strcpy (temp —>Title, B Title); temp ->link=NULL: if (TOP==NULL) Top=Temp; else { temp —>link=Top; TOP==temp; } }

Question 9.
Write the definition of a member function push() for a class Library in C++ to insert a book information in a dynamically allocated strack of books considering the following code is already written as a part of the program

struct book { int bookid; char bookname[20]; book*next; } ; class Library { book*top; public Library() { top=NULL; } void push(); void pop(); void disp() ; -Library(); };

Answer:

void Library: :push() { book*nptr; nptr=new book; cout<<"Enter values for bookid and bookname"; cin> >nptr->bookid; gets(nptr->bookname); nptr->next =NULL; if (top==NULL) top=nptr; else { nptr->next=top, top=nptr; } }

Question 10.
Convert the following Infix expression to its equivalent Postfix expression, showing the stack contents for each step of conversion:
U * V + R / (S-T)
Answer:
U*V + R/(S-T)

OR

OR

Any other method for converting the given Infix expression to its equivalent Postfix expression showing stack contents.