Having milions of points with coordinates (x,y), how would you find points that are at distance at most d from the point given X, Y for every query?

Round 1: Project & Architecture Review (75 mins)Focus: Deep dive into past technical experience.Details: The entire round was dedicated to presenting a personal/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.Questions Asked: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 (guaranteed to exist). 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).