LeetCode-Solutions

Solutions to the LeetCode evergoing problems in Java

Algorithms

• Bit Manipulation
• Array
• String
• Linked List
• Stack
• Queue
• Heap
• Tree
• Hash Table
• Math
• Two Pointers
• Sort
• Recursion
• Binary Search
• Binary Search Tree
• Breadth-First Search
• Depth-First Search
• Backtracking
• Dynamic Programming
• Greedy
• Graph
• Geometry
• Simulation
• Design

BitManipulation

Id	Title	Solution	Time	Space	Difficulty	Note
461	Hamming Distance	Java	O(1)	O(1)	Easy	Thoughtful for max optimisation
476	Number Complement	Java	O(logn)	O(1)	Easy
868	Binary Gap	Java	O(logn)	O(1)	Easy	n is here constant = 32, O(logn) = O(1)
136	Single Number	Java	O(n)	O(1)	Easy
693	Binary Number with Alternating Bits	Java	O(1)	O(1)	Easy
762	Prime Number of Set Bits in Binary Representation	Java	O(R-L)	O(1)	Easy	Good Question

Array

Id	Title	Solution	Time	Space	Difficulty	Note
832	Flipping an Image	Java	O(n*m)	O(1)	Easy	Thoughtful for max optimisation
561	Array Partition I	Java	O(nlogn)	O(1)	Easy
867	Transpose Matrix	Java	O(r*c)	O(r*c)	Easy
806	Number of Lines To Write String	Java	O(n)	O(1)	Easy	n = string length
766	Toeplitz Matrix	Java	O(n*m)	O(1)	Easy
463	Island Perimeter	Java	O(n*m)	O(1)	Easy
412	Fizz Buzz	Java	O(n)	O(1)	Easy
566	Reshape the Matrix	Java	O(n*m)	O(n*m)	Easy
892	Surface Area of 3D Shapes	Java	O(n^2)	O(1)	Easy
485	Max Consecutive Ones	Java	O(n)	O(1)	Easy

String

Id	Title	Solution	Time	Space	Difficulty	Note
709	To Lower Case	Java	O(n)	O(1)	Easy	n is of input
804	Unique Morse Code Words	Java	O(n)	O(n)	Easy	n is sum of all words length
657	Judge Route Circle	Java	O(n)	O(1)	Easy	n is string length
557	Reverse Words in a String III	Java	O(n)	O(n)	Easy	n is of A
344	Reverse String	Java	O(n)	O(n)	Easy	n is of A
821	Shortest Distance to a Character	Java	O(n)	O(n)	Easy	n is of A ; Tricky to think for simplest solution
521	Longest Uncommon Subsequence I	Java	O(min(a,b))	O(1)	Easy	Good puzzle
824	Goat Latin	Java	O(N + W^2)	O(N)	Easy	Good to visualise complexity
443	String Compression	Java	O(n)	O(1)	Easy

LinkedList

Id	Title	Solution	Time	Space	Difficulty	Note
876	Middle of the Linked List	Java	O(n)	O(1)	Easy	fast and slow pointers

Stack

Id	Title	Solution	Time	Space	Difficulty	Note
682	Baseball Game	Java	O(n)	O(n)	Easy
225	Implement Stack using Queues	Java	(O(n) - push, O(1) - rest ops)	O(1)	Easy

Tree

Id	Title	Solution	Time	Space	Difficulty	Note
617	Merge Two Binary Trees	Java	O(n )	O(n)(Worst Case)	Easy	n is min. num of nodes
872	Leaf-Similar Trees	Java	O(n)	O(h)	Easy	h = max height of tree, n = max num of nodes
559	Maximum Depth of N-ary Tree	Java	O(n)	O(h)	Easy	h = max height of tree, n = max num of nodes
590	N-ary Tree Postorder Traversal	Java	O(n)	O(n)	Easy	n = Total num of nodes, Iterative solution is a must
669	Trim a Binary Search Tree	Java	O(n)	O(n)	Easy	n = Total num of nodes
104	Maximum Depth of Binary Tree	Java	O(n)	O(n)	Easy	n = Total num of nodes
589	N-ary Tree Preorder Traversal	Java	O(n)	O(n)	Easy	n = Total num of nodes
226	Invert Binary Tree	Java	O(n)	O(n)	Easy	n = Total num of nodes

HashTable

Id	Title	Solution	Time	Space	Difficulty	Note
771	Jewels and Stones	Java	O(n + m)	O(n)	Easy	n is of J and m is of S
884	Uncommon Words from Two Sentences	Java	O(n + m)	O(n + m)	Easy	n is of A and m is of B
811	Subdomain Visit Count	Java	O(n)	O(n)	Easy	n is of cpDomains
500	Keyboard Row	Java	O(n)	O(n)	Easy	n is of all words length sum
575	Distribute Candies	Java	O(n)	O(n)	Easy	Good question for thinking and optimising
888	Fair Candy Swap	Java	O(n)	O(n)	Easy
496	Next Greater Element I	Java	O(n)	O(n)	Easy	Good question to consider

Math

Id	Title	Solution	Time	Space	Difficulty	Note
883	Projection Area of 3D Shapes	Java	O(n*n)	O(1)	Easy
728	Self Dividing Numbers	Java	O(n)(n = num of numbers between [l,r])	O(n)	Easy	Assuming R is bounded
292	Nim Game	Java	O(1)	O(1)	Easy
812	Largest Triangle Area	Java	O(n^3)	O(1)	Easy	Know formula to solve this
67	Add Binary	Java	O(max(a,b))	O(1)	Easy

Binary Search

Id	Title	Solution	Time	Space	Difficulty	Note
852	Peak Index in a Mountain Array	Java	O(n)	O(1)	Easy
704	Binary Search	Java	O(log(n))	O(1)	Easy

Binary Search Tree

Id	Title	Solution	Time	Space	Difficulty	Note
700	Search in a Binary Search Tree	Java	O(logn)	O(1)	Easy

BFS

Id	Title	Solution	Time	Space	Difficulty	Note
637	Average of Levels in Binary Tree	Java	O(n)	O(m)	Easy	n = total nodes, m = max nodes at any level; Can be solved by DFS as well, Must look
429	N-ary Tree Level Order Traversal	Java	O(n)	O(m)	Easy	n = total nodes, m = max nodes at any level;

DFS

Id	Title	Solution	Time	Space	Difficulty	Note
897	Increasing Order Search Tree	Java	O(n)	O(h)	Easy	n = total nodes, h = max height; Iterative Solution; Bookmarked
112	Path Sum	Java	O(n)	O(h)	Easy	n = total nodes, h = max height;