Memento pattern in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the Memento class that stores the state.

LLD

class Memento:
    def __init__(self, [1]):
        self._state = state

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Asave

Bstate

Cdata

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect parameter names like 'save' or 'data' instead of 'state'.

The Memento class stores the state passed during initialization.

2fill in blank

medium

Complete the code to restore the state from the Memento object.

LLD

class Originator:
    def restore(self, memento):
        self._state = memento.[1]

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A_state

Bstate

Cget_state()

Dsave_state()

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a method that does not exist like get_state() or save_state().

The Originator accesses the stored state directly from the Memento's _state attribute.

3fill in blank

hard

Fix the error in saving the current state into a Memento object.

LLD

class Originator:
    def save(self):
        return Memento([1])

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Astate

Bself.save_state

Cself._state

Dself.state

Attempts:

3 left

💡 Hint

Common Mistakes

Using undefined variables like 'state' or methods like 'save_state'.

The Originator saves its current private state attribute into a new Memento.

4fill in blank

hard

Fill both blanks to implement the Caretaker storing and retrieving mementos.

LLD

class Caretaker:
    def __init__(self):
        self._mementos = []

    def add_memento(self, memento):
        self._mementos.[1](memento)

    def get_memento(self, index):
        return self._mementos[[2]]

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Aappend

Bpop

Cindex

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop to add items or remove to get items by index.

The Caretaker appends mementos to a list and retrieves them by index.

5fill in blank

hard

Fill all three blanks to complete the Originator's state change and memento management.

LLD

class Originator:
    def __init__(self):
        self._state = None

    def set_state(self, state):
        self._state = [1]

    def save(self):
        return Memento(self._state)

    def restore(self, memento):
        self._state = memento.[2]

    def get_state(self):
        return self._state

originator = Originator()
originator.set_state('State1')
memento = originator.save()
originator.set_state('State2')
originator.restore(memento)
print(originator.[3]())

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Astate

B_state

Cget_state

Dsave_state

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect attribute or method names that do not exist.

The Originator sets its state from the parameter, restores from the Memento's _state attribute, and uses get_state() to retrieve the current state.