Problem Roadmap & Study Plan

Knowing the patterns is half the job; the other half is timed repetition until recognizing and coding them is automatic. This page turns the algorithms track into a plan: a roadmap of 179 LeetCode problems grouped by pattern (96 marked ★ core: do these first if time is short), an 8-week schedule, a spaced-repetition routine, and a progress tracker. 134 of the problems are solved step by step, with animations, in the lessons of this track.

1How to Work a Problem

1. Set a timer: 15 minutes for Easy, 25 for Medium, 40 for Hard. Use the method from algorithms/foundations/01-coding_interview_method out loud, even alone.
2. Stuck after a third of the time? Write down what you tried, then read only the approach (not the code) and implement it yourself.
3. Run the tests, then the edge cases, before submitting.
4. Record one line: the pattern and the key insight ("monotonic stack: a warmer day pops colder days"). This line is what you review later.
5. Mark it in the tracker below, with a note to repeat it.

2Spaced Repetition

Re-solve every problem you needed help with after 1, 3, 7 and 21 days, from a blank editor and against the timer. If you solve it cleanly twice in a row, retire it. Most people forget a solution within a week; two clean repeats are what makes the pattern stick in an interview.

3The 8-Week Plan (about 10–15 hours per week)

Short on time? Do only the ★ core problems (96), four per day on six days a week, with the same repetition schedule: about 4 weeks.

Senior candidates: coding rounds are usually Medium-level, but expectations around communication, testing and complexity are higher. Spend the time you save on system design and behavioural preparation.

4Mock Interviews

• Solve with a camera on, or with a person, at least once a week from week 2.
• Use the 45-minute budget: 5 clarify, 5 plan, 20 code, 8 test, 7 discussion.
• Afterwards, score yourself on the five rubric dimensions (problem solving, coding, communication, verification, complexity) and pick one to improve next time.

⚠️ Common Pitfalls

1. Reading solutions instead of solving: recognition is not recall. Always re-solve from a blank editor.
2. Grinding volume without repetition: 150 problems solved once each is worth less than 75 solved three times.
3. Never timing yourself, so interview pace comes as a shock.
4. Practising silently: in interviews you must think out loud.
5. Skipping easy problems: they're where you build speed and clean coding habits.

📋 Quick Reference

Timer: Easy 15 · Medium 25 · Hard 40 minutes
Stuck at 1/3 time → read the approach only → implement yourself
Repeat after 1, 3, 7, 21 days; retire after two clean solves
Core path: ★ problems, 4 per day, ~4 weeks · Full path: 8 weeks

179 problems in pattern order. ★ = core. Links in the last column open the lesson where the problem is solved step by step.

1Progress Tracker

Tick problems as you solve them; progress is saved in this browser.

2The Roadmap by Pattern

Arrays & Hashing

Two Pointers

Sliding Window

Prefix Sums

Stacks & Monotonic Stack

Binary Search

Linked Lists

Intervals

Trees

Binary Search Trees

Heaps & Top-K

Backtracking

Tries

Graphs

Advanced Graphs

1-D Dynamic Programming

2-D Dynamic Programming

Greedy

Math & Matrix

Bit Manipulation

✅ Check yourself

Source: algo_problem_roadmap_and_study_plan_theory_1.md, algo_problem_roadmap_and_study_plan_theory_2.md · generated by tools/build_lessons.py