Reservation and hold system in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the method that reserves an item.

LLD

def reserve_item(self, item_id):
    if self.inventory.[1](item_id):
        self.inventory.remove(item_id)
        return True
    return False

Drag options to blanks, or click blank then click option'

Ais_available

Bcheck_availability

Chas_item

Dcontains

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method that removes the item instead of checking availability.

The method is_available checks if the item is free to reserve.

2fill in blank

medium

Complete the code to hold an item for a user.

LLD

def hold_item(self, item_id, user_id):
    if self.inventory.[1](item_id):
        self.holds[item_id] = user_id
        return True
    return False

Drag options to blanks, or click blank then click option'

Ais_reserved

Bis_locked

Cis_held

Dis_available

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to hold an item that is already reserved or held.

The method is_available ensures the item is free before holding it.

3fill in blank

hard

Fix the error in the method that releases a hold on an item.

LLD

def release_hold(self, item_id):
    if item_id in self.holds:
        [1] self.holds[item_id]
        return True
    return False

Drag options to blanks, or click blank then click option'

Adelete

Bpop

Cremove

Ddiscard

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'remove' which is a list method, not dictionary.

The pop method removes the key and returns its value safely.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps item IDs to user IDs for all held items.

LLD

held_items = { [1]: [2] for [1], [2] in self.holds.items() }

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Aitem_id

Buser_id

Ckey

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same variable name for both key and value.

Use item_id and user_id as variable names for keys and values.

5fill in blank

hard

Fill all three blanks to filter held items where the user ID matches and the hold is still valid.

LLD

valid_holds = { [1]: [2] for [1], [2] in self.holds.items() if self.is_hold_valid([3]) }

Drag options to blanks, or click blank then click option'

Aitem_id

Buser_id

Dhold_id

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the wrong variable to the validity check function.

The comprehension uses item_id and user_id for keys and values, and checks validity by passing item_id.