Algorithm

In mathematics and computer science, an algorithm is an unambiguous specification of how to solve a class of problems. Algorithms can perform calculation, data processing and automated reasoning tasks.

As an effective method, an algorithm can be expressed within a finite amount of space and time and in a well-defined formal language for calculating a function. Starting from an initial state and initial input (perhaps empty), the instructions describe a computation that, when executed, proceeds through a finite number of well-defined successive states, eventually producing "output" and terminating at a final ending state. The transition from one state to the next is not necessarily deterministic; some algorithms, known as randomized algorithms, incorporate random input.

The concept of algorithm has existed for centuries, and the use of the concept can be ascribed to Greek mathematicians, e.g. the sieve of Eratosthenes and Euclid's algorithm; the term algorithm itself derives from the 9th Century mathematician Muḥammad ibn Mūsā al'Khwārizmī, latinized 'Algoritmi'. A partial formalization of what would become the modern notion of algorithm began with attempts to solve the Entscheidungsproblem (the "decision problem") posed by David Hilbert in 1928. Subsequent formalizations were framed as attempts to define "effective calculability" or "effective method"; those formalizations included the Gödel–Herbrand–Kleene recursive functions of 1930, 1934 and 1935, Alonzo Church's lambda calculus of 1936, Emil Post's Formulation 1 of 1936, and Alan Turing's Turing machines of 1936–7 and 1939.

Commons

This is commons algorithm implement, such as sort, find etc.

• Array
• Union Find

Corporation

This is corporation interview algorithm implement, such as alibaba, tencent, baidu etc.

• Alibaba
• Tencent
• Baidu
• Huawei
• Jingdong
• Netease
• Bytedance

LeetCode

The number of LeetCode questions is increasing every week. For more questions and solutions, you can see my Algorithm repository. I'll keep updating for full summary and better solutions. Stay tuned for updates. (Notes: "📖" means you need to subscribe to LeetCode premium membership for the access to premium questions.)

• 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
• Design
• SQL
• Shell Script

Offer

The Pointing Offer.

Corporation

Alibaba

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Tencent

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Baidu

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Huawei

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Jingdong

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Netease

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Bytedance

#	Title	Solution	Time	Space	Difficulty	Tag	Note

LeetCode

Bit Manipulation

#	Title	Solution	Time	Space	Difficulty	Tag	Note
461	Hamming Distance	Java	O(1)	O(1)	Easy

Array

#	Title	Solution	Time	Space	Difficulty	Tag	Note
561	Array Partition I	Java	O(r)	O(r)	Easy
832	Flipping an Image	Java	O(n^2)	O(1)	Easy
867	Transpose Matrix	Java	O(1)	O(1)	Easy

String

#	Title	Solution	Time	Space	Difficulty	Tag	Note
657	Judge Route Circle	Java	O(n)	O(1)	Easy
709	To Lower Case	Java	O(n)	O(1)	Easy
804	Unique Morse Code Words	Java	O(n)	O(n)	Easy

Linked List

#	Title	Solution	Time	Space	Difficulty	Tag	Note
876	Middle of the Linked List	Java	O(n)	O(1)	Easy

Stack

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Heap

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Tree

#	Title	Solution	Time	Space	Difficulty	Tag	Note
617	Merge Two Binary Trees	Java	O(n)	O(h)	Easy

Hash Table

#	Title	Solution	Time	Space	Difficulty	Tag	Note
771	Jewels and Stones	Java	O(m + n)	O(n)	Easy
888	Uncommon Words from Two Sentences	Java	O(m + n)	O(m + n)	Easy

Math

#	Title	Solution	Time	Space	Difficulty	Tag	Note
728	Self Dividing Numbers	Java	O(n)	O(1)	Easy
887	Projection Area of 3D Shapes	Java	O(n^2)	O(1)	Easy

Two Pointers

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Sort

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Recursion

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Binary Search

#	Title	Solution	Time	Space	Difficulty	Tag	Note
852	Peak Index in a Mountain Array	Java	O(logn)	O(1)	Easy

Binary Search Tree

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Breadth-First Search

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Depth-First Search

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Backtracking

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Dynamic Programming

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Greedy

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Graph

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Design

#	Title	Solution	Time	Space	Difficulty	Tag	Note

SQL

#	Title	Solution	Time	Space	Difficulty	Tag	Note

Shell Script

#	Title	Solution	Time	Space	Difficulty	Tag	Note