Question

Create two Java classes called Recursive, RecursiveDemo.

Write four methods

• a- int sum_sqr_rec(stack<int> stk)
  • which will receive a stack of "int" and output the sum of the squares of the elements in the stack.
• b- int plus_minus_rec(stack<int> stk)
  • which will receive a stack of "int" (example: {a,b,c,d,e,f,g,h,i,j}) and output the sum of the elements in the stack as follows:
  • a - b + c - d + e - f + g - h + i -j
• c- void prt_chars_rev_rec(stack<char> stk)
  • which will receive a stack of "char" and print its elements in reverse.
• d- void prt_chars_rec(queue<char> stk) which will receive a queue of "char" and print its elements

Remember to use the stack and queue STL.

Create 2 files:

1. Recursive.java which contains the details of creating the 4 methods as specified above:
   • int sum_sqr_rec(stack<int> stk), (15 points)
   • int plus_minus_rec(stack<int> stk), (15 points)
   • void prt_chars_rev_rec(stack<char> stk), (15 points)
   • void prt_chars_rec(queue<char> stk), (15 points)
2. RecursiveDemo.java which:
   • A- reads a string expression:
     • {(1+2)+[4*(2+3)]}
     • and store the expression in a stack and a queue.(15 points)
     • a- prints the corresponding expression "in reverse" using: prt_chars_rev_rec ( 5 points)
     • b- prints the corresponding expressing "as is" using: prt_chars_rec.( 5 points)
   • B- reads an array of integers: { 1, 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 }
     • and store them in a stack of ints.(5 points)
   • Then it:
   • C- prints the sum of the squares of the elements in the stack using int sum_sqr_rec(stack<int> stk) and outputting the value(5 points):
     • 385
   • D- prints the sum of the elements in the stack using:
     • int plus_minus_rec(stack<int> stk) and outputting the value(5 points):
     • 1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + 9 - 10 = -5

Answer 1

Program code to copy:

// ------------------------------------ Recursive.java ------------------------------------ //

class Recursive {

// --- Defining all 4 methods which are mentioned in statement

// ------------------- Method_1 ------------------------------
// This method will return the sum of all elements of stack by first taking square of them

public int sum_sqr_rec(Stack<Integer> stk){

// --- Declaring a variable to sum the squares of all elements of stack

int sum = 0;

// --- Going through whole stack and squaring each element and then adding in sum

for (int i=0; i<stk.size(); i++){

sum += (stk.get(i) * stk.get(i));
}

// --- Finally return the sum to calling function

return sum;
}

// ------------------- Method_2------------------------------
// This method will add elements of even indices and subtract elements of odd indices in stack

public int plus_minus_rec(Stack<Integer> stk){

int sum = 0;

for (int i=0; i<stk.size(); i++){

if(i % 2 == 0) // --- If index is even add that integer
sum += stk.get(i);
else // --- If it is odd, just subtract that
sum -= stk.get(i);
}

return sum;
}

// ------------------- Method_3------------------------------
// This method will print character elements of stack in reverse order

public void prt_chars_rev_rec(Stack<Character> stk){

System.out.println("The elements of Stack in reverse order are: ");

for (int i=stk.size()-1; i>=0 ; i--) { // --- Just go through whole stack in reverse order from last index to first index

System.out.print(stk.get(i));
}
}

// ------------------- Method_4------------------------------
// This method will print the character elements of queue

public void prt_chars_rec(Queue<Character> stk){

System.out.println("The elements of Queue are: ");

// --- Go through whole queue
// --- Removing each element from queue in order to print it
// --- Until the queue becomes empty

for (int i=0; !stk.isEmpty(); i++){
System.out.print(stk.remove());
}
}
}

// ------------------------------------ RecursiveDemo.java ---------------------------- //

import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

public class RecursiveDemo {

public static void main(String[] args) {

// --- Declaring a String expression as specified in statement

String expression = "{(1+2)+[4*(2+3)]}";

// --- Creating a stack and a queue

Stack<Character> stack = new Stack<>();
Queue<Character> queue = new LinkedList<>();

// --- Iterating through whole String and storing each character in a Stack and a queue

for (int i=0; i<expression.length(); i++){

stack.push(expression.charAt(i));
queue.add(expression.charAt(i));
}

// --- Creating an object of Recursive class

Recursive r = new Recursive();

// --- printing the expression in reverse order by calling prt_chars_rev_rec method

System.out.println();
r.prt_chars_rev_rec(stack);
System.out.println("\n\n============================================\n");

// --- printing the elements as is using prt_chars_rec method

r.prt_chars_rec(queue);
System.out.println("\n\n============================================\n");

// --- Read an array of integers as given in statement and storing them in a stack of ints

int[] array = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

Stack<Integer> ints = new Stack<>();

for (int i=0; i<array.length; i++){
ints.add(array[i]);
}

// --- Calling sum_sqr_rec method to output sum of squared elements

System.out.println("The sum of squares of elements in the Stack is " + r.sum_sqr_rec(ints));
System.out.println("\n============================================\n");

// --- Now printing the sum of elements by calling plus_minus_rec method

System.out.println("The sum of elements of stack is " + r.plus_minus_rec(ints));
System.out.println("\n============================================\n");
}
}

Sample output:

RecursiveDemo x "C:\Program Files\Java\jdk1.8.0_111\bin\java.exe" ... The elements of Stack in reverse order are: }])3+2(*4[+)2+1({ ============================================ The elements of Queue are: {(1+2)+[4*(2+3)]} ============================================ The sum of squares of elements in the Stack is 385 The sum of elements of stack is -5 = ========= ========= ========= ======== ======== Process finished with exit code 0

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