Question

1. Write a recursive method to print the last value in a stack
2. Write a recursive method to reverse the contents of a queue

*java IDE

Answer 1

Dear student, according to the question, the resultant programs are as follows:

Recursive method to Print the Last Value in Stack:

/* Java program to print last value in the stack */
class Stack
{
   static final int SIZE = 10;
   int top;
int a[] = new int[SIZE]; // Maximum size of Stack

Stack() // default constructor to initialize top value
   {
       top = -1;
   }

   void push(int x) // to push value onto stack
   {
       if (top >= (SIZE-1))
       {
           System.out.println("Stack Overflow");
       }
       else
       {
           a[++top] = x;
           System.out.println("element "+ x + " pushed into stack");
       }
   }

   int pop()
   {
       if (top < 0)
       {
           System.out.println("Stack Underflow");
           return 0;
       }
       else
       {
           int x = a[top--];
           return x;
       }
   }
int lastValueInStack(int top) // considering top vaue to get the last value
{
int r;
if(top == 0) // the last value has been stored onto stack at top = 0.
return pop();
else
r = pop();
return lastValueInStack(top-1); // So keep on recursivelly calling till we get top value as 0
}
}

// Main code
class Main
{
   public static void main(String args[])
   {
       Stack s = new Stack();
s.push(1);
       s.push(10);
       s.push(20);
       s.push(30);
   System.out.println(s.lastValueInStack(s.top) + " is the last value from stack");
  
   }
}

Output: