The process consisted of three virtual interviews in a single day, lasting seventy-five minutes each, conducted via MS Teams and HackerRank. The overall experience was positive, highly technical, and deeply focused on data structures, optimisation, and system design.

Round 1: Project & Architecture Review (75 mins)

• Focus: Deep dive into past technical experience.
• Details: The entire round was dedicated to presenting a personal or academic project. The interviewer asked detailed questions regarding the system's architecture, specific algorithmic choices, trade-offs, and design decisions.

Round 2: Coding / Algorithms (75 mins)

• Focus: Problem-solving, bitwise operations, and array manipulation.
• Bitwise Operation (LeetCode 2275 - Largest Combination With Bitwise AND Greater Than Zero): Given an array of integers, find the size of the largest subset where the bitwise AND of all elements is greater than zero.
• Insight: Count the number of set bits (1s) at each of the 32 bit positions across all numbers.
• Frequency Tracking (LeetCode 169 - Majority Element): Given an array, find the element that appears at least $n/2$ times, which is guaranteed to exist. This can be solved using a Hash Map ($O(n)$ space) or optimized using the Boyer-Moore Voting Algorithm ($O(1)$ space).

Round 3: Low-Level Design (LLD) (75 mins)

• Focus: Object-Oriented Design (OOD) and data structure integration.
• Details: Design a parking lot system. The core challenge evolved into choosing the optimal combination of data structures to achieve $O(1)$ efficiency for parking, leaving, and tracking the physical index of each vehicle.
• Key Solution Concept: Integrating a fixed-size array to maintain physical indices, a doubly linked list to manage the pool of free spots, and a Hash Map to map vehicle IDs to list nodes.