LeetCode Solutions (Python)

This repository contains solutions for LeetCode problems I've solved(using Python), links to official(and clever unofficial) solutions.

Solutions are grouped by Topics(see topics folder).

Feel free to Fork, Clone or Star this repository.

Also, check out my JavaScript Repository, which contains JS solutions for all problems below and a lot more.

Difficulty	Title	Tags	My Solutions	LeetCode Solution	Other cool solutions	Solved on my own?	Date
	1. Two Sum	HashTable, Array				Simple HashTable	2019-10-15
	276. Paint Fence	DP, Probability, Math		-	1) Decent explanation	Probability, DP	2019-10-16
	496. Next Greater Element I	Stack, Monotonic Stack, deque				Monotonic Stack	2019-10-17
	1232. Check If It Is a Straight Line	Geometry, Math		-	1) Check slopes, Python "all", 2) Is Triangle area == 0	Formulas: Slopes, Triangle area	2019-10-21
	1233. Remove Sub-Folders from the Filesystem	String, Substring, HashSet, Sorting		-	1) 1. Sort by length -> use HashSet 2. Sort lexic. -> compare only with previous potentian parent	Difficult time/space estim., interesting solutions	2019-10-22
	232. Implement Queue using Stacks	Stack, Queue				2 Stacks(1 reversed) to get amortized O(1) pop	2019-10-22
	674. Longest Continuous Increasing Subsequence	Array, Subseq.		-		Anchor technique, Sliding Window	2019-10-22
	120. Triangle	DP, Bottom-Up DP		-	1) Bottom-up explanation	DP Bottom-up, In-place	2019-10-24
	1022. Sum of Root To Leaf Binary Numbers	Tree, Recursive, Iterative, Stack		-		Stack with Tuple or 2 values, Iterative DFS	2019-10-24
	129. Sum Root to Leaf Numbers	Tree, Recursive, Iterative, Stack		-		Same as #1022	2019-10-24
	124. Binary Tree Maximum Path Sum	Tree, Path, nonlocal, Recursive				Max gain idea: left_sum = max(left_sum, 0), to shorten code	2019-10-25
	1171. Remove Zero Sum Consecutive Nodes from Linked List	LinkedList, HashTable, Prefix Sum, Delete		-	1) Smart two-pass solution (last), 2) Explanation picture	No memory leak in GC, smart two pass	2019-10-29
	733. Flood Fill	Matrix, DFS, BFS, Iterative, Recursive				Good template for DFS, BFS problems	2019-10-29
	443. String Compression	String, Two Pointers				Iterate and check the next to handle last char, Iterate over digits without split	2019-10-29
	138. Copy List with Random Pointer	LinkedList, Default Dict, HashTable, Recursive			1) Awesome use of Default Dict, great one pass, two pass code, 2) O(1) official solution explained	1. No need for new List, store nodes in Dict only 2. Default Dict - create node on the fly	2019-10-30
	594. Longest Harmonious Subseq.	Array, HashTable, Counter, List Compreh., Sorting				Tricky iteration after Sorting, Counter + List Compreh.	2019-11-04
	548. Split Array with Equal Sum	Array, HashTable, Prefix Sum			1) Short Python solutions with "any", "check", slicing, list compreh.	Prefix sums, HashTable, Skip recalculating Zeros	2019-11-06
	1254. Number of Closed Islands	Matrix, BFS, DFS		-		Fill from edges, BFS, DFS	2019-12-12
	121. Best Time to Buy and Sell Stock	Array, Rolling min				Rolling min	2019-12-14
	217. Contains Duplicate	HashTable, Sorting				Sorting = better Space complexity	2019-12-14
	56. Merge Intervals	Intervals, Merging				Sort by start only, compare with last added	2019-12-23
	238. Product of Array Except Self	Array, Prefix Product, Rolling Product				Idea to use prod[i] as product to the left excluding prod[i]	2019-12-30
	53. Maximum Subarray	Array, Kadane, Divide and Conquer				Kadane, Suboptimal non-obvious Divide and Conquer	2020-01-01
	152. Maximum Product Subarray	Array, Rolling Products		-		Rolling Products, swap min and max	2020-01-01
	153. Find Minimum in Rotated Sorted Array	Array, Binary Search				Invariants: 1. [-Inf, left], [right, Inf] ascending 2. min is inside [left, right]	2020-01-01
	33. Search in Rotated Sorted Array	Array, Binary Search			1) Clean Binary Search conditions for one pass	Complex one-pass solution	2020-01-04
	15. 3Sum	Array, Two Pointers		-	1) Sorting, two pointers solution explained	A lot of tricks to stop/skip in the loop	2020-01-04
	11. Container With Most Water	Array, Two Pointers, Area				Two pointers, move shorter	2020-01-05
	371. Sum of Two Integers	Bitwise, Xor, Shift, And, Two's Compl.		-	1) Explanation for 32-bit languages (JS), 2) Python mask fix for infinite bits in two's compl.	Not easy: Xor, Shift, Carry. Python TLE for negative numbers, mask workaround	2020-01-06
	191. Number of 1 Bits	Bitwise				1. check if every bit is 1, or 2. use n &= n - 1 to remove right-most 1	2020-01-06
	268. Missing Number	Bitwise, XOR, Gauss, Arithmetic Progression, Binary Search			1) Binary search solutions (in post and comments)	Xor is best, careful with Binary Search after sorting	2020-01-10
	338. Counting Bits	Bitwise, DP, Remove bit: left, right, meaningful				DP, remove bit from the left, right, right-most 1	2020-01-10
	190. Reverse Bits	Bitwise, Binary, String reverse		-		Handle left-most zeros	2020-01-10
	70. Climbing Stairs	DP				Easy DP	2020-01-21
	322. Coin Change	DP, Top-down, Bottom-up				Top-down, Bottom-up DP	2020-01-21
	300. Longest Increasing Subsequence	DP				Difficult binary search official solution	2020-01-21
	168. Excel Sheet Column Title	String, Convertion, Radix		-	1) Offset by 1: Radix 26: 1-26, Radix 10: 0-9, 2) n -= 1 to get rid of offset, 3) Another good explanation	Offset by 1 in Radix	2020-02-01
	225. Implement Stack using Queues	Queue, Stack				Use queue and rotate	2020-02-03
	269. Alien Dictionary	Graph, Khan, cycle, directed		-	1) Good code, explanation in comments, 2) Decent explanation	Difficult: Khan algo, cycle detection, degree in graph	2020-03-11
	1389. Create Target Array in the Given Order	Array		-		Simple insert	2020-03-22
	1143. Longest Common Subsequence	DP, String, Bottom-up		-		Simple DP, DP space impr.	2020-04-12