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Quick Start

direnv allow        # nix devshell + python 3.14 venv
just test           # 628 tests
just lint           # ruff + mypy strict
just docs           # mkdocs site at localhost:8000

just challenge arrays two_sum     # strip solution → implement
just study arrays                 # watch mode — tests re-run on save
just solution arrays two_sum      # peek if stuck
just challenge-done arrays two_sum
just challenge-progress

Core 42

Topic	#	Drill set
arrays	3	two_sum, group_anagrams, product_except_self
two_pointers	2	three_sum, trapping_rain_water
sliding_window	2	min_window_substring, longest_substring_no_repeat
stacks_queues	2	valid_parentheses, daily_temperatures
searching	2	binary_search, search_rotated_array
linked_lists	2	reverse_linked_list, lru_cache
trees	3	validate_bst, level_order_traversal, trie
graphs	7	dijkstra, a_star, bellman_ford, topo_sort, islands, MST, course_schedule
dp	5	coin_change, edit_distance, knapsack, LIS, LCS
heaps	2	kth_largest, merge_k_sorted_lists
backtracking	3	subsets, combination_sum, n_queens
greedy	2	merge_intervals, jump_game
strings	2	valid_palindrome, longest_palindromic_substring
recursion	2	generate_parentheses, flatten_nested_list
bit_manipulation	1	single_number
sorting	1	quickselect

The remaining 27 implementations stay in the repo as extended practice and reference.

Commands

just                              # list all commands

# ── Testing ──
just test                         # all 628 tests
just practice <topic>             # one topic
just study <topic>                # watch mode
just test-concepts                # concept modules (numpy/scipy/flask/pydantic)

# ── Challenge ──
just challenge <topic> <problem>  # strip solution, show failing tests
just solution <topic> <problem>   # restore solution
just challenge-done <t> <p>       # mark complete
just challenge-progress           # show progress

# ── Quality ──
just lint                         # ruff + mypy strict
just fmt                          # auto-format

# ── Docs ──
just docs                         # mkdocs serve
just pdf-booklet                  # printable reference booklet

Structure

src/algo/         69 implementations, 15 topics (42 core + 27 extended)
src/concepts/     6 modules: t-strings, typing, hypothesis, FFT, Flask, Pydantic
src/practice/     3 code reading + 3 decomposition exercises
tests/            628 tests (pytest + hypothesis)
reference-sheets/ 9 printable reference sheets
docs/             mkdocs site

Reference

• Cross-Reference Guide — pattern → implementation lookup
• Interview Day Guide — printouts, tabs, strategy
• Algorithm Templates — binary search, BFS/DFS, DP, backtracking