Zeni Study

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- Learn Python In 7 Days
  Day 1 : Variable + if/else
  Day 2: Loops
  Day 3 : Array + String
  Day 4 — Functions
  Day 5 — Dictionaries - Hashmap
  Day 6 — Files & Errors
  Day 7 — Mini Project & Programmer Thinking
- Machine Coding:
  Day 1 — Bank account + Wallet :
  Day 2 : RateLimiter + seat booking
  Day 3 : Library Management + Classroom Attendance System
  Day 4 : Bank account and notification system.
  Day 5 : Key-value and payment processor.
  Day 6 : Discount engine + Seat booking( in depth)
  Day 7: Parking lot System :
- Machine coding extended:
  Day 7.5 — Parking Lot (Constraint-Heavy Variant)
  Day 8 : Order + Payment System
  Day 8 — Extension Round (Mid-Interview Change)
  Day 9 — Ticket Booking with Expiry (Simulated Time)
  Day 9 — Extension Round (Seat Lock Ownership + Forced Unlock)
- SQL + DB Thinking course
  Day 1 — Tables, Rows & Thinking in Data
  Day 2 — Relationships & Foreign Keys (Thinking in Connections)
  Day 3 — Filtering, Aggregation & Answering Data Questions
  Day 4 — JOINs (Combining Tables the Right Way)
  Day 5 — Subqueries, EXISTS & NOT EXISTS (Thinking in Layers)
  Day 6 — Indexes, Constraints & How Databases Think
  Day 7 — Full SQL Interview Simulation (SDE-1 Ready)
  Extended Day 1 — Core Business Systems (Deep Practice)
  Extended Day 2 — Booking & Platform Systems (High-Depth Practice)
  Extended Day 3 — Content & Learning Platforms (Capstone Practice)
- LLD: Java
  DAY 1 — Core Foundations (SDE-2 Level)
  DAY 2 — State, Time & Domain Correctness
  DAY 3 — Extensibility & Failure Handling (SDE-2 Core Signal)
  DAY 4 — Concurrency, Scheduling & Consistency (SDE-2 Critical)
  DAY 5 — Workflow Design & Config-Driven Systems (SDE-2+)
  DAY 6 — Eventing & Usage-Based Systems (Advanced SDE-2)
  DAY 7 — Interview Simulation (Hard, Production-Grade)
  Hidden Edge Cases Interviewers Expect (Day-wise)
  Detailed Testing file:
- Assignment:
  If else Practice Set

Zeni Study

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Day 7: Parking lot System :

Explore

Day 7: Parking lot System :

This day is designed to feel exactly like an SDE-1 machine coding round.

⏱ Time-bound

📄 Clear problem statement

🧱 Given structure & signatures

🧪 Deterministic tests

❌ No hints during coding

✅ Focus only on correct implementation

⁠

🟢 Day 7 — Full Machine Coding Simulation (SDE-1 Level)

🎯 Day 7 Objective

By the end of Day 7, the candidate should be able to:

Read a large problem statement

Identify required classes and responsibilities

Implement logic inside given method signatures

Handle multiple interacting objects

Respect constraints & state transitions

Pass all tests within 60–90 minutes

This day answers one question: “Can you clear a real machine coding round?”

⁠

⏱️ Interview Simulation Rules (IMPORTANT)

Give these rules to the candidate before starting:

⏰ Time limit: 90 minutes

❌ Do NOT change class names or method signatures

❌ Do NOT add new public methods

❌ Do NOT modify test file

✅ You may add private helpers if needed

✅ Return values exactly as specified

❌ No print statements in solution

⁠

🧩 The Problem — Parking Lot System (Simplified)

Problem Statement

You are implementing a Parking Lot system.

The system supports:

Multiple parking spots

Parking and un-parking vehicles

Tracking availability

This is a state-heavy, rule-heavy machine coding problem.

⁠

🚗 System Rules

Parking Spot States

Each parking spot can be:

FREE

OCCUPIED

⁠

Vehicle Rules

Each vehicle has a unique vehicle_id

One vehicle occupies one spot

Same vehicle cannot be parked twice

⁠

🧱 Class Definitions (DO NOT MODIFY)

class Vehicle:

def __init__(self, vehicle_id: str):

pass

class ParkingSpot:

def __init__(self, spot_id: int):

pass

def park(self, vehicle: Vehicle) -> bool:

pass

def unpark(self) -> bool:

pass

def is_free(self) -> bool:

pass

def get_vehicle(self):

pass

class ParkingLot:

def __init__(self, total_spots: int):

pass

def park_vehicle(self, vehicle: Vehicle) -> bool:

pass

def unpark_vehicle(self, vehicle_id: str) -> bool:

pass

def get_available_spots(self) -> int:

pass

⁠

📋 Detailed Requirements (READ CAREFULLY)

Vehicle

Store vehicle_id

⁠

ParkingSpot

Initial State

Spot is FREE

No vehicle assigned

park(vehicle)

If spot is already OCCUPIED → return False

Else:

Assign vehicle

Mark as OCCUPIED

Return True

unpark()

If spot is FREE → return False

Else:

Remove vehicle

Mark as FREE

Return True

is_free()

Return True if FREE, else False

get_vehicle()

Return vehicle object if OCCUPIED

Else return None

⁠

ParkingLot

__init__(total_spots)

Create total_spots ParkingSpot objects

Spot IDs should start from 1

park_vehicle(vehicle)

If vehicle already parked → return False

Find the first FREE spot

Park the vehicle

Return True if parked

If no free spot → return False

unpark_vehicle(vehicle_id)

Find spot containing this vehicle

If found:

Unpark it

Return True

If not found → return False

get_available_spots()

Return number of FREE spots

⁠

🧠 Expected Thinking Process (Not Code)

Candidate should think:

ParkingLot manages many ParkingSpots

ParkingSpot manages one Vehicle

Vehicle is a simple data object

State lives inside ParkingSpot

ParkingLot coordinates operations

Must prevent duplicate vehicle parking

⁠

🧪
`solution.py`⁠
(Given to Candidate)

class Vehicle:

def __init__(self, vehicle_id: str):

pass

class ParkingSpot:

def __init__(self, spot_id: int):

pass

def park(self, vehicle: Vehicle) -> bool:

pass

def unpark(self) -> bool:

pass

def is_free(self) -> bool:

pass

def get_vehicle(self):

pass

class ParkingLot:

def __init__(self, total_spots: int):

pass

def park_vehicle(self, vehicle: Vehicle) -> bool:

pass

def unpark_vehicle(self, vehicle_id: str) -> bool:

pass

def get_available_spots(self) -> int:

pass

⁠

🧪 test_day7.py (Evaluation File)

from solution import Vehicle, ParkingLot

def test_parking_lot_basic():

print("Running basic parking tests...")

lot = ParkingLot(2)

v1 = Vehicle("V1")

v2 = Vehicle("V2")

v3 = Vehicle("V3")

assert lot.get_available_spots() == 2

assert lot.park_vehicle(v1) is True

assert lot.get_available_spots() == 1

assert lot.park_vehicle(v2) is True

assert lot.get_available_spots() == 0

assert lot.park_vehicle(v3) is False # no space

print("✅ Basic parking tests passed")

def test_unpark():

print("Running unpark tests...")

lot = ParkingLot(2)

v1 = Vehicle("V1")

v2 = Vehicle("V2")

lot.park_vehicle(v1)

lot.park_vehicle(v2)

assert lot.unpark_vehicle("V1") is True

assert lot.get_available_spots() == 1

assert lot.unpark_vehicle("V1") is False # already removed

assert lot.unpark_vehicle("UNKNOWN") is False

print("✅ Unpark tests passed")

def test_duplicate_vehicle():

print("Running duplicate vehicle tests...")

lot = ParkingLot(2)

v1 = Vehicle("V1")

assert lot.park_vehicle(v1) is True

assert lot.park_vehicle(v1) is False # same vehicle again

print("✅ Duplicate vehicle tests passed")

if __name__ == "__main__":

test_parking_lot_basic()

test_unpark()

test_duplicate_vehicle()

print("\n🎉 ALL DAY 7 TESTS PASSED SUCCESSFULLY")

⁠

✅ Pass Criteria (Strict)

Candidate passes Day 7 if:

All tests pass

No modification to test file

No signature changes

No prints

No global state

Code runs in one go

⁠

🧠 Final Reflection (Must Answer)

How did you break down the problem?

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Day 7: Parking lot System :

🟢 Day 7 — Full Machine Coding Simulation (SDE-1 Level)

🎯 Day 7 Objective

⏱️ Interview Simulation Rules (IMPORTANT)

🧩 The Problem — Parking Lot System (Simplified)

Problem Statement

🚗 System Rules

Parking Spot States

Vehicle Rules

🧱 Class Definitions (DO NOT MODIFY)

📋 Detailed Requirements (READ CAREFULLY)

Vehicle

ParkingSpot

ParkingLot

🧠 Expected Thinking Process (Not Code)

🧪 solution.py⁠ (Given to Candidate)

🧪 test_day7.py (Evaluation File)

✅ Pass Criteria (Strict)

🧠 Final Reflection (Must Answer)

🧪
`solution.py`⁠
(Given to Candidate)