This repository contains 🌟 solutions to various data structure and algorithm problems from LeetCode. All solutions are implemented in Python and are structured for easy understanding and reusability.
A curated list of all LeetCode study plans
Automatic testcase generator for LeetCode problems
- 📂 Each solution is stored in a separate Python file, named according to the problem number and title.
- 🏷️ Organized by category: Arrays, Strings, Trees, Graphs, and more.
📂 .
├── 📁 array
│ ├── 📁 easy
│ │ ├── 1.two_sum.py
│ │ ├── 1346.check_if_n_and_its_double_exist.py
│ │ ├── 1464.maximum_product_of_two_elements_in_an_array.py
│ │ ├── 1480.running_sum_of_1d_array.py
│ │ ├── 1491.average_salary_excluding_the_minimum_and_maximum_salary.py
│ │ ├── 1502.can_make_arithmetic_progression_from_sequence.py
│ │ ├── 1550.three_consecutive_odds.py
│ │ ├── 169.majority_element.py
│ │ ├── 1732.find_the_highest_altitude.py
│ │ ├── 1752.check_if_array_is_sorted_and_rotated.py
│ │ ├── 1800.maximum_ascending_subarray_sum.py
│ │ ├── 1920.build_array_from_permutation.py
│ │ ├── 2176.count_equal_and_divisible_pairs_in_an_array.py
│ │ ├── 2496.maximum_value_of_a_string_in_an_array.py
│ │ ├── 2873.maximum_value_of_an_ordered_triplet_i.py
│ │ ├── 2942.find_words_containing_character.py
│ │ ├── 3105.longest_strictly_increasing_or_strictly_decreasing_subarray.py
│ │ ├── 3151.special_array_i.py
│ │ ├── 3392.count_subarrays_of_length_three_with_a_condition.py
│ │ ├── 448.find_all_numbers_disappeared_in_an_array.py
│ │ ├── 48.rotate_image.py
│ │ ├── 66.plus_one.py
│ │ ├── 747.largest_number_at_least_twice_of_others.py
│ │ └── 896.monotonic_array.py
│ ├── 📁 hard
│ │ └── 41.first_missing_positive.py
│ ├── 📁 medium
│ │ ├── 189.rotate_array.py
│ │ ├── 2780.minimum_index_of_a_valid_split.py
│ │ ├── 2874.maximum_value_of_an_ordered_triplet_ii.py
│ │ ├── 57.insert_interval.py
│ │ └── 915.partition_array_into_disjoint_intervals.py
├── 📁 backtracking
│ ├── 📁 medium
│ │ └── 1980.find_unique_binary_string.py
├── 📁 binary-search
│ ├── 📁 easy
│ │ ├── 1385.find_the_distance_value_between_two_arrays.py
│ │ ├── 1539.kth_missing_positive_number.py
│ │ ├── 2529.maximum_count_of_positive_integer_and_negative_integer.py
│ │ ├── 2540.minimum_common_value.py
│ │ ├── 278.first_bad_version.py
│ │ ├── 35.search_insert_position.py
│ │ ├── 367.valid_perfect_square.py
│ │ ├── 374.guess_number_higher_or_lower.py
│ │ ├── 69.sqrtx.py
│ │ └── 704.binary_search.py
│ ├── 📁 medium
│ │ ├── 153.find_minimum_in_rotated_sorted_array.py
│ │ ├── 1838.frequency_of_the_most_frequent_element.py
│ │ ├── 2226.maximum_candies_allocated_to_k_children.py
│ │ ├── 240.search_a_2d_matrix_ii.py
│ │ ├── 2513.minimize_the_maximum_of_two_arrays.py
│ │ ├── 2594.minimum_time_to_repair_cars.py
│ │ ├── 33.search_in_rotated_sorted_array.py
│ │ ├── 3356.zero_array_transformation_ii.py
│ │ ├── 34.find_first_and_last_position_of_element_in_sorted_array.py
│ │ ├── 74.search_a_2d_matrix.py
│ │ └── 875.koko_eating_bananas.py
├── 📁 binary-tree
│ ├── 📁 easy
│ │ ├── 144.binary_tree_preorder_traversal.py
│ │ ├── 145.binary_tree_postorder_traversal.py
│ │ ├── 404.sum_of_left_leaves.py
│ │ └── 94.binary_tree_inorder_traversal.py
├── 📁 bit-manipulation
│ ├── 📁 easy
│ │ ├── 1009.complement_of_base_10_integer.py
│ │ ├── 1018.binary_prefix_divisible_by_5.py
│ │ ├── 136.single_number.py
│ │ ├── 1486.xor_operation_in_an_array.py
│ │ ├── 191.number_of_1_bits.py
│ │ ├── 231.power_of_two.py
│ │ ├── 268.missing_number.py
│ │ ├── 3304.find_the_k_th_character_in_string_game_i.py
│ │ ├── 342.power_of_four.py
│ │ ├── 389.find_the_difference.py
│ │ └── 476.number_complement.py
│ ├── 📁 medium
│ │ ├── 2401.longest_nice_subarray.py
│ │ ├── 2425.bitwise_xor_of_all_pairings.py
│ │ ├── 2429.minimize_xor.py
│ │ ├── 2683.neighboring_bitwise_xor.py
│ │ └── 3191.minimum_operations_to_make_binary_array_elements_equal_to_one_i.py
├── 📁 breadth-first-search
│ ├── 📁 medium
│ │ ├── 102.binary_tree_level_order_traversal.py
│ │ ├── 103.binary_tree_zigzag_level_order_traversal.py
│ │ ├── 107.binary_tree_level_order_traversal_ii.py
│ │ ├── 1161.maximum_level_sum_of_a_binary_tree.py
│ │ ├── 1609.even_odd_tree.py
│ │ ├── 429.n_ary_tree_level_order_traversal.py
│ │ ├── 515.find_largest_value_in_each_tree_row.py
│ │ └── 662.maximum_width_of_binary_tree.py
├── 📁 counting
│ ├── 📁 easy
│ │ ├── 1512.number_of_good_pairs.py
│ │ ├── 1790.check_if_one_string_swap_can_make_strings_equal.py
│ │ └── 3442.maximum_difference_between_even_and_odd_frequency_i.py
│ ├── 📁 medium
│ │ └── 2131.longest_palindrome_by_concatenating_two_letter_words.py
├── 📁 design
│ ├── 📁 hard
│ │ └── 381.insert_delete_getrandom_o1_duplicates_allowed.py
│ ├── 📁 medium
│ │ └── 380.insert_delete_getrandom_o1.py
├── 📁 divide-and-conquer
│ ├── 📁 easy
│ │ └── 1763.longest_nice_substring.py
├── 📁 dynamic-programming
│ ├── 📁 easy
│ │ └── 509.fibonacci_number.py
│ ├── 📁 medium
│ │ ├── 122.best_time_to_buy_and_sell_stock_ii.py
│ │ ├── 1749.maximum_absolute_sum_of_any_subarray.py
│ │ └── 53.maximum_subarray.py
├── 📁 geometry
│ ├── 📁 easy
│ │ └── 1232.check_if_it_is_a_straight_line.py
├── 📁 greedy-algorithm
│ ├── 📁 easy
│ │ ├── 2900.longest_unequal_adjacent_groups_subsequence_i.py
│ │ ├── 3074.apple_redistribution_into_boxes.py
│ │ └── 680.valid_palindrome_ii.py
│ ├── 📁 medium
│ │ ├── 1007.minimum_domino_rotations_for_equal_row.py
│ │ ├── 1282.group_the_people_given_the_group_size_they_belong_to.py
│ │ ├── 2091.removing_minimum_and_maximum_from_array.py
│ │ ├── 2116.check_if_a_parentheses_string_can_be_valid.py
│ │ ├── 2918.minimum_equal_sum_of_two_arrays_after_replacing_zeros.py
│ │ ├── 452.minimum_number_of_arrows_to_burst_balloons.py
│ │ ├── 646.maximum_length_of_pair_chain.py
│ │ ├── 781.rabbits_in_forest.py
│ │ └── 921.minimum_add_to_make_parentheses_valid.py
├── 📁 hash-table
│ ├── 📁 easy
│ │ ├── 1128.number_of_equivalent_domino_pairs.py
│ │ ├── 1207.unique_number_of_occurrences.py
│ │ ├── 1399.count_largest_group.py
│ │ ├── 1436.destination_city.py
│ │ ├── 2006.count_number_of_pairs_with_absolute_difference_k.py
│ │ ├── 205.isomorphic_strings.py
│ │ ├── 217.contains_duplicate.py
│ │ ├── 219.contains_duplicate_ii.py
│ │ ├── 2206.divide_array_into_equal_pairs.py
│ │ ├── 2404.most_frequent_even_element.py
│ │ ├── 3375.minimum_operations_to_make_array_values_equal_to_k.py
│ │ ├── 3396.minimum_number_of_operations_to_make_elements_in_array_distinct.py
│ │ ├── 383.ransom_note.py
│ │ └── 575.distribute_candies.py
│ ├── 📁 medium
│ │ ├── 1400.construct_k_palindrome_strings.py
│ │ ├── 1726.tuple_with_same_product.py
│ │ ├── 1930.unique_length_3_palindromic_subsequences.py
│ │ ├── 2364.count_number_of_bad_pairs.py
│ │ ├── 2657.find_the_prefix_common_array_of_two_arrays.py
│ │ ├── 3159.find_occurrences_of_an_element_in_an_array.py
│ │ ├── 3160.find_the_number_of_distinct_colors_among_the_balls.py
│ │ ├── 3223.minimum_length_of_string_after_operations.py
│ │ ├── 49.group_anagrams.py
│ │ └── 916.word_subsets.py
├── 📁 heap-priority-queue
│ ├── 📁 easy
│ │ ├── 2558.take_gifts_from_the_richest_pile.py
│ │ └── 3065.minimum_operations_to_exceed_threshold_value_i.py
│ ├── 📁 hard
│ │ └── 295.find_median_from_data_stream.py
│ ├── 📁 medium
│ │ ├── 2342.max_sum_of_a_pair_with_equal_sum_of_digits.py
│ │ ├── 2349.design_a_number_container_system.py
│ │ ├── 3066.minimum_operations_to_exceed_threshold_value_ii.py
│ │ └── 451.sort_characters_by_frequency.py
├── 📁 linked-list
│ ├── 📁 easy
│ │ ├── 1290.convert_binary_number_in_a_linked_list_to_integer.py
│ │ ├── 141.linked_list_cycle.py
│ │ ├── 206.reverse_linked_list.py
│ │ ├── 234.palindrome_linked_list.py
│ │ ├── 83.remove_duplicates_from_sorted_list.py
│ │ └── 876.middle_of_the_linked_list.py
│ ├── 📁 medium
│ │ ├── 142.linked_list_cycle_ii.py
│ │ ├── 143.reorder_list.py
│ │ ├── 2095.delete_the_middle_node_of_a_linked_list.py
│ │ ├── 61.rotate_list.py
│ │ ├── 82.remove_duplicates_from_sorted_list_ii.py
│ │ └── 92.reverse_linked_list_ii.py
├── 📁 math
│ ├── 📁 easy
│ │ ├── 1217.minimum_cost_to_move_chips_to_the_same_position.py
│ │ ├── 1281.subtract_the_product_and_sum_of_digits_of_an_integer.py
│ │ ├── 1295.find_numbers_with_even_number_of_digits.py
│ │ ├── 1523.count_odd_numbers_in_an_interval_range.py
│ │ ├── 1588.sum_of_all_odd_length_subarrays.py
│ │ ├── 1822.sign_of_the_product_of_an_array.py
│ │ ├── 2520.count_the_digits_that_divide_a_number.py
│ │ ├── 2566.maximum_difference_by_remapping_a_digit.py
│ │ ├── 2843.count_symmetric_integers.py
│ │ ├── 2894.divisible_and_non_divisible_sums_difference.py
│ │ ├── 2965.find_missing_and_repeated_values.py
│ │ ├── 3024.type_of_triangle.py
│ │ ├── 326.power_of_three.py
│ │ └── 9.palindrome_number.py
│ ├── 📁 medium
│ │ ├── 1780.check_if_number_is_a_sum_of_powers_of_three.py
│ │ └── 2579.count_total_number_of_colored_cells.py
├── 📁 matrix
│ ├── 📁 easy
│ │ ├── 1572.matrix_diagonal_sum.py
│ │ ├── 1672.richest_customer_wealth.py
│ │ ├── 2133.check_if_every_row_and_column_contains_all_numbers.py
│ │ ├── 2643.row_with_maximum_ones.py
│ │ └── 566.reshape_the_matrix.py
│ ├── 📁 medium
│ │ ├── 2661.first_completely_painted_row_or_column.py
│ │ └── 73.set_matrix_zeroes.py
├── 📁 monotonic-stack
│ ├── 📁 easy
│ │ ├── 1475.final_prices_with_a_special_discount_in_a_shop.py
│ │ └── 496.next_greater_element_i.py
│ ├── 📁 medium
│ │ ├── 2487.remove_nodes_from_linked_list.py
│ │ ├── 402.remove_k_digits.py
│ │ ├── 503.next_greater_element_ii.py
│ │ ├── 739.daily_temperatures.py
│ │ └── 907.sum_of_subarray_minimums.py
├── 📁 prefix-sum
│ ├── 📁 easy
│ │ ├── 1854.maximum_population_year.py
│ │ ├── 2574.left_and_right_sum_differences.py
│ │ ├── 2848.points_that_intersect_with_cars.py
│ │ ├── 303.range_sum_query_immutable.py
│ │ ├── 3354.make_array_elements_equal_to_zero.py
│ │ ├── 3427.sum_of_variable_length_subarrays.py
│ │ └── 3432.count_partitions_with_even_sum_difference.py
│ ├── 📁 medium
│ │ ├── 1352.product_of_the_last_k_numbers.py
│ │ ├── 1769.minimum_number_of_operations_to_move_all_balls_to_each_box.py
│ │ ├── 2121.intervals_between_identical_elements.py
│ │ ├── 2145.count_the_hidden_sequences.py
│ │ ├── 2270.number_of_ways_to_split_array.py
│ │ ├── 2381.shifting_letters_ii.py
│ │ ├── 2559.count_vowel_strings_in_ranges.py
│ │ ├── 2615.sum_of_distances.py
│ │ ├── 3355.zero_array_transformation_i.py
│ │ ├── 523.continuous_subarray_sum.py
│ │ ├── 525.contiguous_array.py
│ │ ├── 560.subarray_sum_equals_k.py
│ │ └── 974.subarray_sums_divisible_by_k.py
├── 📁 sliding-window
│ ├── 📁 easy
│ │ ├── 2379.minimum_recolors_to_get_k_consecutive_black_blocks.py
│ │ ├── 3206.alternating_groups_i.py
│ │ └── 643.maximum_average_subarray_i.py
│ ├── 📁 medium
│ │ ├── 1004.max_consecutive_ones_iii.py
│ │ ├── 1358.number_of_substrings_containing_all_three_characters.py
│ │ ├── 187.repeated_dna_sequences.py
│ │ ├── 209.minimum_size_subarray_sum.py
│ │ ├── 2461.maximum_sum_of_distinct_subarrays_with_length_k.py
│ │ ├── 2799.count_complete_subarrays_in_an_array.py
│ │ ├── 3.longest_substring_without_repeating_characters.py
│ │ ├── 3208.alternating_groups_ii.py
│ │ ├── 424.longest_repeating_character_replacement.py
│ │ ├── 438.find_all_anagrams_in_a_string.py
│ │ ├── 567.permutation_in_string.py
│ │ ├── 713.subarray_product_less_than_k.py
│ │ └── 904.fruit_into_baskets.py
├── 📁 sorting
│ ├── 📁 easy
│ │ ├── 1636.sort_array_by_increasing_frequency.py
│ │ ├── 2099.find_subsequence_of_length_k_with_the_largest_sum.py
│ │ ├── 2164.sort_even_and_odd_indices_independently.py
│ │ └── 3194.minimum_average_of_smallest_and_largest_elements.py
│ ├── 📁 medium
│ │ ├── 1887.reduction_operations_to_make_the_array_elements_equal.py
│ │ ├── 2033.minimum_operations_to_make_a_uni_value_grid.py
│ │ ├── 2294.partition_array_such_that_maximum_difference_is_k.py
│ │ ├── 2785.sort_vowels_in_a_string.py
│ │ ├── 2966.divide_array_into_arrays_with_max_difference.py
│ │ ├── 3085.minimum_deletions_to_make_string_k_special.py
│ │ ├── 3169.count_days_without_meetings.py
│ │ ├── 3394.check_if_grid_can_be_cut_into_sections.py
│ │ ├── 3443.maximum_manhattan_distance_after_k_changes.py
│ │ ├── 347.top_k_frequent_elements.py
│ │ ├── 442.find_all_duplicates_in_an_array.py
│ │ ├── 462.minimum_moves_to_equal_array_elements_ii.py
│ │ └── 56.merge_intervals.py
├── 📁 stack
│ ├── 📁 easy
│ │ ├── 1047.remove_all_adjacent_duplicates_in_string.py
│ │ ├── 1544.make_the_string_great.py
│ │ ├── 20.valid_parentheses.py
│ │ └── 3174.clear_digits.py
│ ├── 📁 medium
│ │ ├── 1081.smallest_subsequence_of_distinct_characters.py
│ │ ├── 1209.remove_all_adjacent_duplicates_in_string_ii.py
│ │ ├── 150.evaluate_reverse_polish_notation.py
│ │ ├── 155.min_stack.py
│ │ ├── 1910.remove_all_occurrences_of_a_substring.py
│ │ ├── 2390.removing_stars_from_a_string.py
│ │ ├── 316.remove_duplicate_letters.py
│ │ └── 71.simplify_path.py
├── 📁 string
│ ├── 📁 easy
│ │ ├── 13.roman_to_integer.py
│ │ ├── 1309.decrypt_string_from_alphabet_to_integer_mapping.py
│ │ ├── 1422.maximum_score_after_splitting_a_string.py
│ │ ├── 1446.consecutive_characters.py
│ │ ├── 1678.goal_parser_interpretation.py
│ │ ├── 1832.check_if_the_sentence_is_pangram.py
│ │ ├── 1961.check_if_string_is_a_prefix_of_array.py
│ │ ├── 2124.check_if_all_as_appears_before_all_bs.py
│ │ ├── 2129.capitalize_the_title.py
│ │ ├── 2138.divide_a_string_into_groups_of_size_k.py
│ │ ├── 2255.count_prefixes_of_a_given_string.py
│ │ ├── 242.valid_anagram.py
│ │ ├── 2490.circular_sentence.py
│ │ ├── 3120.count_the_number_of_special_characters_i.py
│ │ ├── 387.first_unique_character_in_a_string.py
│ │ ├── 58.length_of_last_word.py
│ │ ├── 709.to_lower_case.py
│ │ └── 953.verifying_an_alien_dictionary.py
│ ├── 📁 medium
│ │ ├── 2384.largest_palindromic_number.py
│ │ ├── 3121.count_the_number_of_special_characters_ii.py
│ │ ├── 38.count_and_say.py
│ │ └── 8.string_to_integer_atoi.py
├── 📁 string-matching
│ ├── 📁 easy
│ │ ├── 1408.string_matching_in_an_array.py
│ │ └── 28.find_the_index_of_the_first_occurrence_in_a_string.py
├── 📁 tree
│ ├── 📁 easy
│ │ ├── 589.n_ary_tree_preorder_traversal.py
│ │ └── 590.n_ary_tree_postorder_traversal.py
├── 📁 trie
│ ├── 📁 easy
│ │ ├── 1455.check_if_a_word_occurs_as_a_prefix_of_any_word_in_a_sentence.py
│ │ ├── 2185.counting_words_with_a_given_prefix.py
│ │ └── 3042.count_prefix_and_suffix_pairs_i.py
├── 📁 two-pointers
│ ├── 📁 easy
│ │ ├── 125.valid_palindrome.py
│ │ ├── 1768.merge_strings_alternately.py
│ │ ├── 202.happy_number.py
│ │ ├── 2200.find_all_k_distant_indices_in_an_array.py
│ │ ├── 2460.apply_operations_to_an_array.py
│ │ ├── 2570.merge_two_2d_arrays_by_summing_values.py
│ │ ├── 26.remove_duplicates_from_sorted_array.py
│ │ ├── 27.remove_element.py
│ │ ├── 2824.count_pairs_whose_sum_is_less_than_target.py
│ │ ├── 283.move_zeroes.py
│ │ ├── 344.reverse_string.py
│ │ ├── 345.reverse_vowels_of_a_string.py
│ │ ├── 3467.transform_array_by_parity.py
│ │ ├── 541.reverse_string_ii.py
│ │ ├── 844.backspace_string_compare.py
│ │ ├── 88.merge_sorted_array.py
│ │ ├── 905.sort_array_by_parity.py
│ │ ├── 922.sort_array_by_parity_ii.py
│ │ └── 977.squares_of_a_sorted_array.py
│ ├── 📁 medium
│ │ ├── 11.container_with_most_water.py
│ │ ├── 15.3sum.py
│ │ ├── 16.3sum_closest.py
│ │ ├── 167.two_sum_ii_input_array_is_sorted.py
│ │ ├── 18.4sum.py
│ │ ├── 2161.partition_array_according_to_given_pivot.py
│ │ ├── 2563.count_the_number_of_fair_pairs.py
│ │ ├── 287.find_the_duplicate_number.py
│ │ ├── 457.circular_array_loop.py
│ │ ├── 581.shortest_unsorted_continuous_subarray.py
│ │ ├── 75.sort_colors.py
│ │ ├── 80.remove_duplicates_from_sorted_array_ii.py
│ │ └── 986.interval_list_intersections.py
├── LICENSE
├── README.md
├── TODO.md
├── directory_layout_script.py
├── lowercase_folder_names.py
├── problem_description_script.py
├── replace_dash_with_underscore_in_filenames.py
├── requirements.txt
└── safe_fix_leetcode_ids.py
💡 Pro Tip: Click the filenames to view each solution directly on GitHub!
| 📂 Category | 📜 Description |
|---|---|
| 📊 Arrays | Searching, sorting, subarray sums, and more. |
| 🧵 Strings | String manipulations, substrings, and pattern matching. |
| 🔗 Linked Lists | Singly, doubly linked list problems. |
| 🌲 Trees | Binary trees, search trees, and n-ary trees. |
| 🗺️ Graphs | Traversals, shortest paths, and connectivity. |
| 🚀 Dynamic Programming | Optimal substructure and overlapping subproblems. |
Each solution file contains:
- Problem Description: A detailed explanation of the problem, its constraints, and examples.
- Test Cases: Example inputs and expected outputs.
- Python Implementation: The function or class implementing the solution.
- Time and Space Complexity Analysis: A brief analysis of the efficiency of the solution.
Example:
"""
Problem Number: 1. Two Sum
Difficulty Level: Easy
https://leetcode.com/problems/two-sum/
********************************************************************************
Given an array of integers nums and an integer target, return indices of the two numbers
such that they add up to target. You may assume that each input would have exactly one
solution, and you may not use the same element twice. You can return the answer in any order
Example 1:
Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].
Example 2:
Input: nums = [3,2,4], target = 6
Output: [1,2]
Example 3:
Input: nums = [3,3], target = 6
Output: [0,1]
Constraints:
2 <= nums.length <= 10^4
-10^9 <= nums[i] <= 10^9
-10^9 <= target <= 10^9
Only one valid answer exists.
"""
from typing import List
class Solution:
def twoSum(self, nums: List[int], target: int) -> List[int]:
pairs = dict()
for idx, num in enumerate(nums):
if target - num in pairs:
return [pairs[target - num], idx]
pairs[num] = idx
# Time Complexity: O(n)
# Space Complexity: O(n)