The Algorithm Study Plan: Master LeetCode in 90 Days

LeetCode has over 3,000 problems. Solving all of them is neither necessary nor efficient. The most successful interview candidates solve 150-200 carefully selected problems that cover the core patterns. This 90-day plan organizes those problems into a progressive curriculum that builds pattern recognition, not just problem-solving ability. The goal is not to memorize solutions — it is to develop the ability to recognize which pattern applies to a new problem and implement it under time pressure.

The plan divides 90 days into six phases of 15 days each, progressing from fundamental data structures through advanced algorithmic techniques. Each phase has specific problem targets, time benchmarks, and pattern recognition goals. Expect to spend 2-3 hours daily. Consistency matters more than marathon sessions — your brain needs sleep to consolidate pattern recognition.

Phase 1 (Days 1-15): Arrays, Strings, and Hash Maps. These are the most commonly tested data structures. Master the two-pointer technique, sliding window, prefix sums, and hash map lookups. Target: solve 30 problems (15 easy, 15 medium). Time benchmark: easy problems in under 15 minutes, medium in under 30 minutes. Key patterns include finding pairs that sum to a target, maximum subarray problems, and string manipulation with hash maps for frequency counting.

Phase 2 (Days 16-30): Linked Lists, Stacks, and Queues. Linked list problems test pointer manipulation skills. Stack problems appear frequently in parsing and evaluation questions. Master the slow/fast pointer technique, stack-based expression evaluation, and monotonic stack patterns. Target: 25 problems (10 easy, 15 medium). Key problems include reversing a linked list in groups, validating parentheses, and implementing a min-stack.