Park Plus Backend Developer Interview Questions and Answers

Round duration - 90 minutes
Round difficulty - Hard

Timing was late evening. Platform was good.

Q1. 
Largest Cycle in Maze Problem Statement
Given a maze represented by 'N' cells numbered from 0 to N-1, and an array arr of 'N' integers where arr[i] denotes the cell number that can be reached from the 'i'...read more
Ans. 
Identify the length of the largest cycle in a maze represented by cells and an array of integers.
• Iterate through each cell and find the cycle length using DFS or Floyd's Tortoise and Hare algorithm.

• Handle self-cycles and cells with no exit by checking arr[i] = i and arr[i] = -1 respectively.

• Output the length of the largest cycle found or -1 if no cycles exist.
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Q2. 
Ninja and the Maze Problem Statement
Ninja is stuck in a maze represented as a 2D grid. He can move in four directions (Up, Down, Left, Right) until he hits a wall ('1'). Once stopped, he can choose a new...read more
Ans. 
Determine if Ninja can reach the destination in a maze by moving in four directions until hitting a wall.
• Create a function to traverse the maze using depth-first search or breadth-first search.

• Keep track of visited cells to avoid infinite loops.

• Return 'True' if destination is reachable, 'False' otherwise.
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Q1. What is a multithreaded environment, and how would you develop an application that can run in that environment without any issues?
Ans. 
A multithreaded environment allows multiple threads to execute concurrently, improving application performance and responsiveness.
• Thread Management: Use thread pools to manage threads efficiently, reducing overhead from frequent thread creation and destruction.

• Synchronization: Implement synchronization mechanisms (like mutexes or semaphores) to prevent race conditions when accessing shared resources.

• Concurrency Control...read more
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Q2. What locking mechanisms are used in a multithreaded environment to prevent deadlock in critical sections?
Ans. 
Locking mechanisms in multithreaded environments prevent deadlock by managing access to critical sections effectively.
• Mutexes: A mutual exclusion lock that allows only one thread to access a resource at a time, preventing race conditions.

• Semaphores: A signaling mechanism that controls access to a resource by maintaining a count, allowing multiple threads to access it up to a limit.

• Read/Write Locks: These allow multiple...read more
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Computer Fundamentals

Q1. Flatten a binary tree
Ans. 
Flatten a binary tree by converting it into a linked list in-place.
• Use a recursive approach to flatten the binary tree.

• Traverse the tree in a pre-order manner and keep track of the previous node.

• Set the left child of each node to null and the right child to the next node in the linked list.

• Example: Input: 1 -> 2 -> 5 -> 3 -> 4 -> null, Output: 1 -> null -> 2 -> null -> 3 -> null -> 4 -> null -> 5 -> null
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Easy to medium, can solve with leetcode medium

Q1. Number of islands count
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Q2. First and last index of a particular element in an array
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