Queue

# Menu Driven Program: Shuttlecock Box using Queue (FIFO).
# Queue concept:
# - ENQUEUE: add shuttlecock at REAR end
# - DEQUEUE: remove shuttlecock from FRONT end
# - PEEK: view shuttlecock at FRONT without removing
# - Underflow: trying to DEQUEUE from empty queue

def enqueue(q, item):
  # Insert at REAR
  q.append(item)

def isEmpty(q):
  return len(q) == 0

def dequeue(q):
  # Delete from FRONT
  if not isEmpty(q):
      return q.pop(0)
  else:
      return None  # Underflow situation

def peek(q):
  # View FRONT element
  if not isEmpty(q):
      return q[0]
  else:
      return None

def size(q):
  return len(q)

def display(q):
  # Display queue from FRONT to REAR
  if isEmpty(q):
      print("Box is empty.")
  else:
      print("Shuttlecocks in box (FRONT -> REAR):", q)

# Main Program (Menu Driven)
box = list()  # this is our queue

while True:
  print("\n--- SHUTTLECOCK BOX MENU (QUEUE / FIFO) ---")
  print("1. Add shuttlecock (ENQUEUE)")
  print("2. Remove shuttlecock (DEQUEUE)")
  print("3. See next shuttlecock (PEEK)")
  print("4. Box size (SIZE)")
  print("5. Display box")
  print("6. Exit")

  choice = int(input("Enter your choice: "))

  if choice == 1:
      code = input("Enter shuttlecock code/name to add: ")
      enqueue(box, code)
      print(code, "added at REAR.")

  elif choice == 2:
      removed = dequeue(box)
      if removed is None:
          print("Queue Underflow: Box is empty, cannot remove.")
      else:
          print("Removed from FRONT:", removed)

  elif choice == 3:
      front_item = peek(box)
      if front_item is None:
          print("Box is empty (nothing at FRONT).")
      else:
          print("Next shuttlecock at FRONT is:", front_item)

  elif choice == 4:
      print("Number of shuttlecocks in box:", size(box))

  elif choice == 5:
      display(box)

  elif choice == 6:
      print("Exiting program...")
      break

  else:
      print("Invalid choice. Try again.")

--- SHUTTLECOCK BOX MENU (QUEUE / FIFO) ---
1. Add shuttlecock (ENQUEUE)
2. Remove shuttlecock (DEQUEUE)
3. See next shuttlecock (PEEK)
4. Box size (SIZE)
5. Display box
6. Exit
Enter your choice: 1
Enter shuttlecock code/name to add: YONEX-1
YONEX-1 added at REAR.

--- SHUTTLECOCK BOX MENU (QUEUE / FIFO) ---
1. Add shuttlecock (ENQUEUE)
2. Remove shuttlecock (DEQUEUE)
3. See next shuttlecock (PEEK)
4. Box size (SIZE)
5. Display box
6. Exit
Enter your choice: 5
Shuttlecocks in box (FRONT -> REAR): ['YONEX-1']

--- SHUTTLECOCK BOX MENU (QUEUE / FIFO) ---
1. Add shuttlecock (ENQUEUE)
2. Remove shuttlecock (DEQUEUE)
3. See next shuttlecock (PEEK)
4. Box size (SIZE)
5. Display box
6. Exit
Enter your choice: 2
Removed from FRONT: YONEX-1

--- SHUTTLECOCK BOX MENU (QUEUE / FIFO) ---
1. Add shuttlecock (ENQUEUE)
2. Remove shuttlecock (DEQUEUE)
3. See next shuttlecock (PEEK)
4. Box size (SIZE)
5. Display box
6. Exit
Enter your choice: 6
Exiting program...

# Palindrome check using DEQUE (implemented using list)
# Algorithm idea (as in the book):
# 1) Insert all characters using INSERTREAR
# 2) Remove one char from FRONT and one from REAR
# 3) Compare them until deque becomes empty or has 1 char

def insertRear(dq, ch):
    dq.append(ch)

def deletionFront(dq):
    return dq.pop(0)

def deletionRear(dq):
    return dq.pop()

# Main Program
s = input("Enter a string: ")

# Create deque and insert characters at REAR (like normal queue)
dq = list()
for ch in s:
    insertRear(dq, ch)

is_palindrome = True

# Compare FRONT and REAR characters
while len(dq) > 1:
    front_ch = deletionFront(dq)
    rear_ch = deletionRear(dq)

    if front_ch != rear_ch:
        is_palindrome = False
        break

if is_palindrome:
    print('The word "' + s + '" is a palindrome')
else:
    print('The word "' + s + '" is not a palindrome')

Enter a string: madam
The word "madam" is a palindrome

Enter a string: hello
The word "hello" is not a palindrome