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Software Engineering Interview Prep Guide

A structured collection of LeetCode problem walkthroughs, coding patterns, and system design concepts for SDE/SWE technical interviews at top tech companies.

What This Guide Covers​

  • LeetCode problem walkthroughs — step-by-step solutions with time/space complexity analysis
  • Core data structures — arrays, linked lists, trees, graphs, heaps, hash maps
  • Algorithm patterns — sliding window, two pointers, BFS/DFS, dynamic programming, binary search
  • System design concepts — available via the System Design blog series

Start with these foundational problems before tackling the harder ones:

  1. Arrays and hashing: Longest Consecutive Sequence
  2. Trees: Maximum Depth of Binary Tree → Same Tree → Level Order Traversal
  3. Dynamic programming: Pascal's Triangle → Triangle → Best Time to Buy and Sell Stock
  4. Graphs: Path Sum → Critical Connections

Frequently Asked Questions​

How many LeetCode problems do I need to solve to pass coding interviews? Most candidates recommend 75–150 problems covering all major patterns. Focus on understanding the pattern, not memorizing solutions — companies like FAANG test variations, not exact problems.

What coding patterns appear most often in interviews? The most common are: sliding window, two pointers, BFS/DFS on trees/graphs, dynamic programming (knapsack, LCS), binary search, and topological sort. Each pattern covers dozens of problems.

How long does it take to prepare for a coding interview? Most people need 2–4 months of consistent daily practice (1–2 hours/day) to feel prepared for mid-level SDE roles. Senior roles add system design preparation (another 4–6 weeks).

Do I need to know system design for SDE-1 interviews? It depends on the company. Most FAANG-equivalent companies include a light system design round even for SDE-1. Start with the basics: REST APIs, database indexing, caching, and load balancing.

Index of LeetCode Problems​