Question

1. Write a c program to calculate the factorial of a number using recursion    [8]

Question five

1. Write a stack algorithm to POP an item                                                         [6]
2. What does FRONT and REAR signify in a queue?                                                                 [6]
3. Write an algorithm for a dequeue operation                                                                       [8]

Answer 1

Write a c program to calculate the factorial of a number using recursion .

#include <stdio.h>
int factorial(int n);
int main()
{
int n;
printf("Enter a positive integer: ");
scanf("%d", &n);
printf("Factorial of %d = %d", n, factorial(n));
return 0;
}
int factorial(int n)
{
if (n >= 1)
return n*factorial(n-1);
else
return 1;
}

Write a stack algorithm to POP an item

 function pop: stack

   if stack is empty
      return null
   endif
   
   data ← stack[top]
   top ← top - 1
   return data

end 

Function://implementation

int pop(int data) {

   if(!isempty()) {
      data = stack[top];
      top = top - 1;   
      return data;
   } else {
      printf("Could not retrieve data, Stack is empty.\n");
   }
}

What does FRONT and REAR signify in a queue?  

Front and rear variables point to the position from where insertions and deletions are performed in a queue. Initially, the value of front and queue is -1 which represents an empty queue. Array representation of a queue containing 5 elements along with the respective values of front and rea

A	B	C	D	E
0	1	2	3	4	5
FRONT				REAR

FRONT POINTS TO A

REAR POINTS TO E

Write an algorithm for a dequeue operation       

function dequeue
   
   if queue is empty
      return underflow
   end if

   data = queue[front]
   front ← front + 1
   return true

end function

Implementation

int dequeue() {
   if(isempty())
      return 0;

   int data = queue[front];
   front = front + 1;

   return data;
}