Introduction

These are my solutions to Leetcode problems in Java 8. I have tried to keep the solutions clear and concise, but there might be opportunities for improvement. In that case, just send me a PR.

Problems tagged Easy

Problem ID	Problem	Solution	Space Complexity	Time Complexity	Runtime (ms)
832	Flipping an image	Click	O(m*n)	O(1)	8
824	Goat Latin	Click	O(n)	O(1)	95
830	Positions of Large Groups	Click	O(n)	O(1)	19
821	Shortest Distance to a Character	Click	O(n)	O(1)	9
819	Most Common Word	Click	O(n)	O(n)	84
811	Subdomain Visit Count	Click	O(n)	O(n)	116
806	Number of Lines to Write String	Click	O(n)	O(1)	3
804	Unique Morse Code Words	Click	O(n)	O(1)	11
796	Rotate String	Click	O(n)	O(1)	4
788	Rotated Digits	Click	O(2^N * N)	O(1)	214
784	Letter Case Permutation	Click	O(2 ^ n)	O(2 ^ n) for returning, else O(1)	97
783	Minimum Distance Between BST Nodes	Click	O(n)	O(1)	5
771	Jewels and stones	Click	O(n)	O(1)	19
695	Max Area of Island	Click	O(m * n)	O(m * n)	37
203	Remove linked list elements	Click	O(n)	O(1)	7
122	Best Time to Buy and Sell Stock II	Click	O(n)	O(1)	2
121	Best Time to Buy and Sell Stock	Click	O(n)	O(1)	1
111	Minimum Depth of Binary Tree	Click	O(n)	O(1)	0
20	Valid Parentheses	Click	O(n)	O(1)	58

Problems tagged Medium

Problem ID	Problem	Solution	Space Complexity	Time Complexity	Runtime (ms)
799	Champagne Tower	Click	O(m * n)	O(m * n)	29
791	Custom Sort String	Click	O(n log n)	O(1)	92
785	Is Graph Bipartite?	Click	O(V+E)	O(V)	9
779	k-th-symbol-in-grammar	Click	O(n)	O(1)	5
769	Max Chunks to Make Sorted	Click	O(n)	O(1)	4
767	Reorganize String	Click	O(n)	O(1)	11
764	Largest Plus Sign	Click	O(N ^ 2)	O(N ^ 2)	162
763	Partition Labels	Click	O(n)	O(1)	13
756	Pyramid Transition Matrix	Click	Exponential	O(n)	28
547	Friend Circles	Click	O(n log n)	O(n)	13
449	Serialize and Deserialize BST	Click	O(n)	O(n)	110
332	Reconstruct Itinerary	Click	O(n^2)	O(n)	13
207	Course Schedule	Click	O(V + E)	O(V)	10
200	Number of Islands	Click	O(m * n)	O(m * n)	7
130	Surrounded Regions	Click	O(m * n)	O(m * n)	6
127	Word Ladder	Click	O(n)	O(n)	459
107	Binary Tree Level Order Traversal II	Click	O(n)	O(n)	98
103	Binary Tree Zigzag Level Order Traversal	Click	O(n)	O(n)	73
102	Binary Tree Level Order Traversal	Click	O(n)	O(n)	66
100	Same Tree	Click	O(n)	O(1)	3
94	Binary Tree Inorder Traversal	Click	O(n)	O(n)	0
64	Minimum Path Sum	Click	O(m * n)	O(m * n)	8
63	Unique Paths II	Click	O(m * n)	O(m * n)	1
62	Unique Paths	Click	O(m * n)	O(m * n)	1
17	Letter Combinations of a Phone Number	Click	O(n)	O(1)	46
3	Longest Substring Without Repeating Characters	Click	O(n)	O(n)	35
2	Add Two Numbers	Click	O(n)	O(1)	60

Problems tagged Hard

Problem ID	Problem	Solution	Space Complexity	Time Complexity	Runtime (ms)
765	Couples Holding Hands	Click	O(n)	O(n)	5
297	Serialize and Deserialize Binary Tree	Click	O(n)	O(n)	17
72	Edit Distance	Click	O(m * n)	O(m * n)	14
23	Merge k Sorted Lists	Click	O(n)	O(1)	14