Daily Drill¶

42 core algorithms. All of them. Every day. Seven days.

Challenge mode strips each implementation, leaving the signature and docstring. You re-implement from scratch and run tests to verify.

How It Works¶

just challenge <topic> <problem>  # strip solution → you implement
just study <topic>                # watch mode — re-runs tests on save
just solution <topic> <problem>   # restore if stuck
just challenge-done <t> <p>       # mark complete
just challenge-progress           # see stats

The 42¶

Copy-paste the full block to strip all 42 at once, or work topic by topic.

Arrays (3)¶

just challenge arrays two_sum
just challenge arrays group_anagrams
just challenge arrays product_except_self

Two Pointers (2)¶

just challenge two_pointers three_sum
just challenge two_pointers trapping_rain_water

Sliding Window (2)¶

just challenge sliding_window min_window_substring
just challenge sliding_window longest_substring_no_repeat

Stacks & Queues (2)¶

just challenge stacks_queues valid_parentheses
just challenge stacks_queues daily_temperatures

Searching (2)¶

just challenge searching binary_search
just challenge searching search_rotated_array

Linked Lists (2)¶

just challenge linked_lists reverse_linked_list
just challenge linked_lists lru_cache

Trees (3)¶

just challenge trees validate_bst
just challenge trees level_order_traversal
just challenge trees trie

Graphs (7)¶

just challenge graphs number_of_islands
just challenge graphs topological_sort
just challenge graphs course_schedule
just challenge graphs dijkstra
just challenge graphs a_star_search
just challenge graphs bellman_ford
just challenge graphs minimum_spanning_tree

Dynamic Programming (5)¶

just challenge dp coin_change
just challenge dp edit_distance
just challenge dp knapsack
just challenge dp longest_increasing_subseq
just challenge dp longest_common_subseq

Heaps (2)¶

just challenge heaps kth_largest
just challenge heaps merge_k_sorted_lists

Backtracking (3)¶

just challenge backtracking subsets
just challenge backtracking combination_sum
just challenge backtracking n_queens

Greedy (2)¶

just challenge greedy merge_intervals
just challenge greedy jump_game

Strings (2)¶

just challenge strings valid_palindrome
just challenge strings longest_palindromic_substring

Recursion (2)¶

just challenge recursion generate_parentheses
just challenge recursion flatten_nested_list

Bit Manipulation (1)¶

just challenge bit_manipulation single_number

Sorting (1)¶

just challenge sorting quickselect

Tracking¶

After each pass, mark status:

Mark	Meaning
	From memory, under 25 min
	Needed a hint or slow
	Could not solve

Re-drill all and problems first the next day.

just challenge-progress

Extended Practice¶

The remaining 27 implementations are in the repo for deeper study:

graphs: clone_graph, word_ladder, network_delay_time, network_flow, geohash_grid, kd_tree
dp: climbing_stairs, traveling_salesman_dp, constraint_satisfaction
arrays: top_k_frequent
two_pointers: container_with_most_water
stacks_queues: min_stack
searching: find_minimum_rotated
linked_lists: merge_two_sorted
trees: max_depth, invert_tree
heaps: task_scheduler
backtracking: permutations
greedy: interval_scheduling
strings: valid_anagram, longest_common_prefix, string_to_integer_atoi
recursion: pow_x_n, letter_combinations_phone, tower_of_hanoi
bit_manipulation: counting_bits, reverse_bits
sorting: merge_sort_inversions
patterns: sliding_window (max_sum_subarray)

Use just challenge <topic> <problem> on any of these the same way.

Tips¶

Talk out loud while solving — practice interview communication
25 min per problem is interview pace
If you can't identify the pattern in 3 min, check the decision tree