leetcode

LeetCode Solutions

Algorithm solutions organized by difficulty level. Each file includes a problem description, approach explanation, complexity analysis, and test cases.

Easy

#	Problem	Approach	Solution
1	Two Sum	Hash map	1_two_sum.py
9	Palindrome Number	Math	9_palindrome_number.py
20	Valid Parentheses	Stack	20_valid_parentheses.py
35	Search Insert Position	Binary search	35_search_insert_position.py
53	Maximum Subarray	Kadane's algorithm	53_maximum_subarray.py
67	Add Binary	Math	67_add_binary.py
70	Climbing Stairs	Dynamic programming	70_climbing_stairs.py
83	Remove Duplicates from Sorted List	Linked list	83_remove_duplicates_from_sorted_list.py
88	Merge Sorted Array	Two pointers	88_merge_sorted_array.py
118	Pascal's Triangle	Dynamic programming	118_pascals_triangle.py
121	Best Time to Buy and Sell Stock	One pass	121_best_time_to_buy_and_sell_stock.py
136	Single Number	XOR bit manipulation	136_single_number.py
141	Linked List Cycle	Floyd's tortoise & hare	141_linked_list_cycle.py
169	Majority Element	Boyer-Moore voting	169_majority_element.py
190	Reverse Bits	Bit manipulation	190_reverse_bits.py
206	Reverse Linked List	Iterative pointers	206_reverse_linked_list.py
217	Contains Duplicate	Hash set	217_contains_duplicate.py
226	Invert Binary Tree	Recursion	226_invert_binary_tree.py
231	Power of Two	Bit manipulation	231_power_of_two.py
242	Valid Anagram	Character counting	242_valid_anagram.py
2824	Count Pairs Less Than Target	Brute force	2824_count_pairs.py
—	Design an Ordered Stream	Array	design_an_ordered_stream.py
—	Jewels and Stones	Hash set	jewels_and_stones.py
—	Number of Good Pairs	Counting	number_of_goods_pairs.py
—	Roman to Integer	Hash map	roman_to_integer.py
—	Single Row Keyboard	Hash map	single_row_keyboard.py

Medium

#	Problem	Approach	Solution
3	Longest Substring Without Repeating Characters	Sliding window	3_longest_substring_without_repeating.py
11	Container With Most Water	Two pointers	11_container_with_most_water.py
15	3Sum	Sort + two pointers	15_three_sum.py
33	Search in Rotated Sorted Array	Modified binary search	33_search_in_rotated_sorted_array.py
36	Valid Sudoku	Hash sets	36_valid_sudoku.py
49	Group Anagrams	Sorted key hash map	49_group_anagrams.py
56	Merge Intervals	Sort + merge	56_merge_intervals.py
102	Binary Tree Level Order Traversal	BFS	102_binary_tree_level_order_traversal.py
152	Maximum Product Subarray	Track min/max	152_maximum_product_subarray.py
200	Number of Islands	DFS flood fill	200_number_of_islands.py
238	Product of Array Except Self	Prefix/suffix products	238_product_of_array_except_self.py

Hard

#	Problem	Approach	Solution
23	Merge k Sorted Lists	Min-heap	23_merge_k_sorted_lists.py
42	Trapping Rain Water	Two pointers	42_trapping_rain_water.py
76	Minimum Window Substring	Sliding window	76_minimum_window_substring.py
124	Binary Tree Maximum Path Sum	DFS	124_binary_tree_maximum_path_sum.py
295	Find Median from Data Stream	Two heaps	295_find_median_from_data_stream.py