Posted on Feb 2, 2021 • Edited on Jun 25, 2021

Leetcode Solutions Index

This is the master index for my series of Leetcode solution explanations. If you like these solutions or found them useful, please like this post.

Hard Problem Solutions:

#	TITLE	RELATED TOPICS
32	Longest Valid Parentheses	Stack
51	N-Queens	Backtracking, DFS, Recursion, Bit Manipulation
52	N-Queens II	Backtracking, DFS, Recursion, Bit Manipulation
65	Valid Number	String
164	Maximum Gap	Bucket Sort, Math
329	Longest Increasing Path in a Matrix	Recursion, DFS, Memoization
336	Palindrome Pairs	Map
354	Russian Doll Envelopes	LIS, Binary Search, DP
630	Course Schedule III	Priority Queue, Heap
745	Prefix and Suffix Search	Trie
778	Swim in Rising Water	Dijkstra's, Priority Queue, Heap
871	Minimum Number of Refueling Stops	Max Priority Queue, Max Heap, Greedy
895	Maximum Frequency Stack	Frequency Map, Stack
906	Super Palindromes	Math, Palindromes
936	Stamping The Sequence	Character Mask
968	Binary Tree Cameras	DFS, Recursion
987	Vertical Order Traversal of a Binary Tree	Tree, DFS, Recursion, Bit Manipulation
1074	Number of Submatrices That Sum to Target	Matrix, Map
1192	Critical Connections in a Network	Tarjan's
1354	Construct Target Array With Multiple Sums	Priority Queue, Heap
1383	Maximum Performance of a Team	Priority Queue, Heap
1713	Minimum Operations to Make a Subsequence	LCS, LIS, Binary Search
1735	Count Ways to Make Array With Product	Math
1739	Building Boxes	Math

Medium Problem Solutions:

#	TITLE	RELATED TOPICS
11	Container With Most Water	Sliding Window
12	Integer to Roman	Math
17	Letter Combinations of a Phone Number	DFS, Recursion
19	Remove Nth Node From End of List	Linked List
22	Generate Parentheses	Recursion, Bit Manipulation
29	Divide Two Integers (ver. 1)	Bit Manipulation
29	Divide Two Integers (ver. 2)	Math
31	Next Permutation	Array, Math
34	Find First and Last Position of Element in Sorted Array	Binary Search
45	Jump Game II	Array
48	Rotate Image	Matrix
63	Unique Paths II	Matrix, DP
71	Simplify Path	Stack, Sliding Window
86	Partition List	Linked List
102	Binary Tree Level Order Traversal	Binary Tree, BFS, Level-Order, Queue
105	Construct Binary Tree from Preorder and Inorder Traversal	Binary Tree, Preorder, Inorder, Recursion
109	Convert Sorted List to Binary Search Tree	Tree, Linked List, In-Order, Recursion, Floyd's
114	Flatten Binary Tree to Linked List	Binary Tree, Pre-Order, Recursion
120	Triangle	DP
128	Longest Consecutive Sequence	Map, Array
138	Copy List with Random Pointer	Linked List
150	Evaluate Reverse Polish Notation	Math, Stack
199	Binary Tree Right Side View	Tree, BFS, DFS, Recursion
240	Search a 2D Matrix II	Matrix, Binary Search
284	Peeking Iterator	Class
304	Range Sum Query 2D - Immutable	Matrix, DP, Prefix Sum
318	Maximum Product of Word Lengths	Bit Manipulation
322	Coin Change	DFS, Recursion
341	Flatten Nested List Iterator	Class, Queue, Recursion
376	Wiggle Subsequence	Subsequence
377	Combination Sum IV	DP
413	Arithmetic Slices	Math
417	Pacific Atlantic Water Flow	DFS, Recursion, DP
423	Reconstruct Original Digits from English	Frequency Map
462	Minimum Moves to Equal Array Elements II	Math, Array
473	Matchsticks to Square	Backtracking, Recursion
474	Ones and Zeros	DP
478	Generate Random Point in a Circle	Math
524	Longest Word in Dictionary through Deleting	String
535	Encode and Decode TinyURL	Map
538	Convert BST to Greater Tree	Tree, Inorder
554	Brick Wall	Frequency Map
576	Out of Boundary Paths	DP
581	Shortest Unsorted Continuous Subarray	Array
583	Delete Operation for Two Strings	LCS, DP
609	Find Duplicate File in System	Map, String
622	Design Circular Queue	Linked List
623	Add One Row to Tree	Binary Tree, DFS, Recursion
647	Palindromic Substrings	Math
665	Non-decreasing Array	Array
667	Beautiful Arrangement II	Math
669	Trim a Binary Tree	Tree, Recursion
684	Redundant Connection	Union-Find, Graph
695	Max Area of Island	Matrix, DFS, Recursion
714	Best Time to Buy and Sell Stock with Transaction Fee	State Machine
729	My Calendar I	Class, Linked List
752	Open the Lock	Graph, BFS, Queue
775	Global and Local Inversions	Math
784	Letter Case Permutation	Recursion, DFS
785	Is Graph Bipartite?	BFS, Bit Manipulation
795	Number of Subarrays with Bounded Maximum	Math, Array
816	Ambiguous Coordinates	String
820	Short Encoding of Words (ver. 1)	Set
820	Short Encoding of Words (ver. 2)	Trie
823	Binary Trees With Factors	Binary Tree, Map, Math
841	Keys and Rooms	DFS
856	Score of Parentheses	Binary, Math
869	Reordered Power of 2	Math
870	Advantage Shuffle	Array
890	Find and Replace Pattern	Map, Mask
916	Word Subsets	Frequency Map
923	3Sum With Multiplicity	Frequency Map, Combinatorics
946	Validate Stack Sequences	Stack, 2-Pointer
966	Vowel Spellchecker	Map, Set, Masking
970	Powerful Integers	Set
971	Flip Binary Tree To Match Preorder Traversal	Binary Tree, DFS, Recursion
991	Broken Calculator	Math
1048	Longest String Chain	Set, Map, DP
1091	Shortest Path in Binary Matrix	BFS, Matrix, Bit Manipulation
1209	Remove All Adjacent Duplicates in String II	Recursion, Stack
1249	Minimum Remove to Make Valid Parentheses	Stack
1268	Search Suggestions System	2-Pointer System
1302	Deepest Leaves Sum	BFS, Queue, DFS, Recursion
1329	Sort the Matrix Diagonally	Matrix
1396	Design Underground System	Class, Map
1423	Maximum Points You Can Obtain from Cards	Sliding Window
1461	Check If a String Contains All Binary Codes of Size K	Binary, Bit Manipulation
1465	Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts	Array, Math
1551	Minimum Operations to Make Array Equal	Math
1631	Path With Minimum Effort	BFS, Dijkstra's, Heap
1642	Furthest Building You Can Reach	Heap
1663	Smallest String With A Given Numeric Value	Math
1673	Find the Most Competitive Subsequence	Stack
1675	Minimize Deviation in Array	Heap
1680	Concatenation of Consecutive Binary Numbers	Binary, Bit Manipulation
1690	Stone Game VII	DP
1695	Maximum Erasure Value	Array, Sliding Window
1696	Jump Game VI	DP, Deque, In-Place, Sliding Window
1717	Maximum Score From Removing Substrings (ver. 1)	DP, Stack
1717	Maximum Score From Removing Substrings (ver. 2)	String
1721	Swapping Nodes in a Linked List	Linked List
1734	Decode XORed Permutation	Bitwise XOR, Math
1737	Change Minimum Characters to Satisfy One of Three Conditions	Frequency Map, Math
1738	Find Kth Largest XOR Coordinate Value	Bitwise XOR, DP, Heap, Math

Easy Problem Solutions:

#	TITLE	RELATED TOPICS
13	Roman to Integer	Math
118	Pascal's Triangle	Array, Math
141	Linked List Cycle	Linked List, Floyd's
160	Intersection of Two Linked Lists	Linked List
204	Count Primes	Math
242	Valid Anagram	Frequency Map
243	Palindrome Linked List	Linked List, Floyd's
268	Missing Number	Math
326	Power of Three	Math
509	Fibonacci Number	Math
589	N-ary Tree Preorder Traversal	Recursion, DFS
594	Longest Harmonious Subsequence	Frequency Map
595	Distribute Candies	Set
637	Average of Levels in Binary Tree	Binary Tree, BFS
645	Set Mismatch (ver. 1)	Array, Math
645	Set Mismatch (ver. 2)	Array, Math
696	Count Binary Substrings	String, Math
706	Design HashMap (ver. 1)	Map, Array
706	Design HashMap (ver. 2)	Hashing Function, Linked List
709	To Lower Case	String
746	Min Cost Climbing Stairs	DP, Array
821	Shortest Distance to a Character	DP
953	Verifying an Alien Dictionary	Map
1332	Remove Palindromic Subsequences	String
1337	The K Weakest Rows in a Matrix (ver. 1)	Matrix
1337	The K Weakest Rows in a Matrix (ver. 2)	Matrix, Binary Search, Heap, Bit Manipulation
1342	Number of Steps to Reduce a Number to Zero	Math
1480	Running Sum of 1d Array	Prefix Sum
1704	Determine if String Halves Are Alike	String
1710	Maximum Units on a Truck	Sort, Array

Top comments (2)

Rafael Sousa • Mar 8 '21

Pretty cool Sean. I'll definitely keep eyes on this series.
Actually, I'll make it better. I'll study one of them a day.

Thanks!

seanpgallivan • Mar 8 '21

You're welcome, Rafael!

I've been doing the daily leetcode challenge problem pretty much every day for the past 8 months, and I will definitely agree that a little bit each day really helps!