Algorithm/System Design Practice

Supported Language

• Java
• Python
• C++
• Swift
• Javascript
• Scala
• Go

Miscellaneous

easy

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Binary Watch	Solution Test	Solution Test	Solution Test	Solution Test	Solution Test	Solution Test	Solution Test
Roman Digits	Solution Test	Solution Test	Solution Test	Solution Test	Solution Test		Solution Test
Valid Anagram	Solution Test	Solution Test	Solution Test	Solution Test	Solution Test	Solution Test	Solution Test

Medium

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Pouring Water	Solution Test
RankTeams	Solution Test

Hard

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Best Time to Buy and Sell Stock(I, II, III, IV, Cooldown, Fee)	Solution Test		Solution Test	Solution Test
List Of List Iterator	Solution Test
Iterable Iterator	Solution Test

Array

easy

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Rotate Array	Solution Test	Solution Test	Solution Test			Solution Test	Solution Test
Reverse Vowels of a String	Solution Test	Solution Test					Solution Test
Move Zero	Solution Test						Solution Test

Medium

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Zigzag Conversion	Solution Test	Solution Test	Solution Test	Solution Test	Solution Test	Solution Test	Solution Test
Subarray Sums Divisible by K	Solution Test
Number of Students Doing Homework at a Given Time	Solution Test
Make Two Arrays Equal by Reversing Sub-arrays	Solution Test
Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts	Solution Test
Diagonal Traverse II	Solution Test
Advance Shuffle	Solution Test
Bubble Switcher II III	Solution Test
Invalid Transaction	Solution Test
Randomize Collection	Solution Test
Reduce Array Size to Half	Solution Test
Sum Subarray Minimums	Solution Test
Find All Duplicates in an Array Solution Test
Check If All 1's Are at Least Length K Places Away	Solution Test
Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold	Solution Test
Unique Paths I II	Solution Test
Array of Doubled Pairs	Solution Test
Get Equal Substrings Within Budget	Solution Test
Maximum Points You Can Obtain from Cards	Solution Test
Count Servers that Communicate	Solution Test
Longest Turbulent Subarray	Solution Test
Queries on a Permutation With Key	Solution Test
Count Number of Teams	Solution Test
Cinema Seat Allocation	Solution Test
Friends Of Appropriate Ages	Solution Test
Global and Local Inversions	Solution Test
Sum of Mutated Array Closest to Target	Solution Test
Lonely Pixel I II	Solution Test
Construct Binary Tree from Inorder and Postorder Traversal	Solution Test
Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	Solution Test
Subarray Sum Equals K	Solution Test
Maximum Sum Circular Subarray	Solution Test
Divide Array in Sets of K Consecutive Numbers	Solution Test
Grumpy Bookstore Owner	Solution Test
Corporate Flight Bookings	Solution Test
Queens That Can Attack the King	Solution Test
Remove Sub-Folders from the Filesystem	Solution Test
Uncrossed Lines	Solution Test
Longest Line of Consecutive One in Matrix	Solution Test
Split Array with Equal Sum	Solution Test
Teemo Attacking	Solution Test
Number of Subarrays with Bounded Maximum	Solution Test
Minimum Increment to Make Array Unique	Solution Test
Leftmost Column with at Least a One	Solution Test
Previous Permutation With One Swap	Solution Test
Decrease Elements To Make Array Zigzag	Solution Test
Count Square Submatrices with All Ones	Solution Test
Sort the Matrix Diagonally	Solution Test
Subrectangle Queries	Solution Test
Reveal Cards In Increasing Order	Solution Test
Task Scheduler	Solution Test
Count Triplets That Can Form Two Arrays of Equal XOR	Solution Test
Array Nesting	Solution Test
Shortest Word Distance III	Solution Test
Maximum Sum of Two Non-Overlapping Subarrays	Solution Test
Filter Restaurants by Vegan-Friendly, Price and Distance	Solution Test
Beautiful Arrangement I II	Solution Test
Capacity To Ship Packages Within D Days	Solution Test
Best Sightseeing Pair	Solution Test
Minimum Domino Rotations For Equal Row	Solution Test
Number of Matching Subsequences	Solution Test
Candy Crush	Solution Test
Combination Sum II III	Solution Test
Range Addition	Solution Test
Snapshot Array	Solution Test
Max Area of Island	Solution Test
Avoid Flood in The City	Solution Test
Design Twitter	Solution Test

Hard

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Remove duplicates int from array	Solution Test	Solution Test	Solution Test			Solution Test	Solution Test
Print Pattern	Solution Test		Solution Test				Solution Test
Sliding Windows	Solution Test		Solution Test				Solution Test
Minimum Size Subarray Sum	Solution Test
Continuous Subarray Sum	Solution Test
Subarray Product Less Than K	Solution Test		Solution Test
Longest Palindrome Length		Solution Test
Merge Intervals		Solution Test
Wiggle Sort	Solution Test
Brick Wall	Solution
Next Greater Element	Solution Test
Search for a Range	Solution Test
1-bit and 2-bit Characters	Solution Test
Count of Smaller Numbers After Self		Solution Test
Insert Interval	Solution Test	Solution Test
Word Search						Solution Test
Intersection of Arrays	Solution Test	Solution Test				Solution Test
Longest Consecutive Sequence			Solution Test
Largest Number			Solution Test
Candies			Solution Test
Water			Solution Test
Gas Station			Solution Test
Implement queue with array	Solution Test
Most Population Year
Replace Elements with Greatest Element on Right Side	Solution Test
Reverse Only Letters	Solution Test
Pour Water	Solution Test
Find Smallest Letter Greater Than Target	Solution Test
Maximum Width Ramp	Solution Test
Pancake Sorting	Solution Test

Matrix

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Minimum steps to G(Facebook)	Solution Test
Rotate Image	Solution Test					Solution Test
Spiral Matrix II	Solution Test		Solution Test
Number of Islands	Solution Test		Solution Test
Set Zeroes			Solution Test
Search I			Solution Test
Search II			Solution Test
Mine Sweeper	Solution Test

Linked List

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Circle	Solution Test						Solution Test
Remove reverse kth element	Solution Test
One diff only(Facebook)	Solution Test
Swap Pairs	Solution Test
Reorder List	Solution Test
Odd Even Linked List	Solution Test
Reverse Nodes in k-Group	Solution Test
Print Immutable Linked List in Reverse	Solution Test

Stack

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Min Stack(Netflix)	Solution Test	Solution Test	Solution Test
Wiggle Subsequence	Solution Test		Solution Test
Max Chunks To Make Sorted			Solution Test
Calculator			Solution Test

Math

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Add One(Apple)	Solution Test	Solution Test	Solution Test		Solution Test	Solution Test	Solution Test
Sort by one(GE)	Solution Test	Solution Test	Solution Test		Solution Test	Solution Test	Solution Test
Reverse Integer	Solution Test		Solution Test
One's Number	Solution		Solution Test
Add Two Numbers	Solution Test		Solution Test
ATOI	Solution Test		Solution Test
Sum(Two Sum, Three Sum, Three Sum Closest, 4 Sum)	Solution Test
Ugly Number	Solution Test		Solution Test
Count Numbers with Unique Digits	Solution Test
Prime Sum(Facebook)	Solution Test
Big Integer(Facebook)	Solution Test
Single Number	Solution Test
Arranging Coins			Solution Test
Perfect Number						Solution Test	Solution Test
Prime Number of Set Bits in Binary Representation							Solution Test
Sequential Digits	Solution Test

Bit Operation

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Power Of Four	Solution Test		Solution Test			Solution Test	Solution Test
Single Number	Solution Test	Solution Test	Solution Test			Solution Test	Solution Test
Swap Two Integer	Solution Test	Python use tuple	Solution Test	Swift use tuple		Scala use tuple

Tree

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Binrary Tree Serialization(Apple)	Solution Test
Binrary Tree Traversal	Solution Test		Solution [Test]	Solution Test)
Minimum Height Trees	Solution Test
Longest Consecutive Path	Solution Test
Binary Tree Zigzag Level Order Traversal	Solution Test
Find Duplicate Subtrees	Solution Test
Longest Path(Facebook)	Solution Test
Balanced Binrary Tree		Solution Test
Add One Row to Tree	Solution Test
Construct String from Binary Tree		Solution Test
Range Sum of BST	Solution Test
Path Sum III	Solution Test
Find Largest Value in Each Tree Row	Solution Test
Deepest Leaves Sum	Solution Test

String

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Knuth–Morris–Pratt	Solution Test	Solution Test	Solution Test				Solution Test
Longest Substring Without Repeating Characters	Solution Test
Isomorphic Strings	Solution Test	Solution Test
Reverse Words	Solution Test					Solution Test	Solution Test
Interleave(Facebook)	Solution Test
Count cross for reorder array		Solution Test
Minimum Time Difference	Solution Test
Remove K Digits	Solution Test
Minimum Window Substring	Solution Test
Z Sort	Solution Test		Solution Test
Remove Duplicate Letters	Solution Test		Solution Test
Top K Frequent Words			Solution Test
Decode String			Solution Test
Minimum Window Substring			Solution Test
String Matching	Solution Test
Custom Sort String	Solution Test
Shortest Completing Word	Solution Test
Push Dominoes	Solution Test

Permutation

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Permutation(Apple)	Solution Test	Solution Test				Solution Test

Greedy

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Permutation(Apple)	Solution Test

Hint: When it asking maximum, minmum, optimal, this could be a dynamic programming problem

Problem List	Difficulty	Java	Python	C++	Swift	JavaScript	Scala	Go
Fibonacci	Solution Test	Solution Test	Solution Test				Solution Test
Coin Change	Solution Test		Solution Test
Knapsack	Solution Test		Solution Test
Longest Common Subsequence(Linkedin)	Solution Test		Solution Test
Subset to Sum	Solution Test		Solution Test
Maximal Square	Solution Test
Longest Increasing Subsequence	Solution Test
Largest Rectangle in Histogram	Solution Test
Wildcard Matching	Solution Test
Predict Winner	Solution Test
2 Keys Keyboard	Solution Test
Edit Distance	Solution Test		Solution Test
Print House	Solution Test		Solution Test
Maximum Length of Repeated Subarray	Solution Test
Marbles in Three Baskets	Solution Test
Split Array With Same Average			Solution Test
Distinct Subsequences Total			Solution Test
Decode Ways II	Solution Test
Min Cost Climbing Stairs	Solution Test
heapest Flights Within K Stops	Solution Test

Binary Search

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Binary Search in rotated order array	Solution Test		Solution Test				Solution Test
Lookup Latest Good Version(Facebook)	Solution Test
Random Color(Uber)	Solution Test

Graph

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Topology Sort(Apple)	Solution Test
Dijkstra Algorithm	Solution Test
Minimum Spanning Tree(Prim, Krusal)	Solution Test

Geometry

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Valid Triangle Number	Solution Test
Max Points on a Line	Solution Test

Data Structure

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Trie	Solution Test
LRU(Salesforce/Amazon)	Solution Test
LFU	Solution Test
Binary Heap	Solution Test		Solution Test
Magic Dictionary	Solution Test		Solution Test
Map Sum Pairs	Solution Test
Find Median from Data Stream			Solution Test
Fenwick Tree			Solution Test
Range Module	Solution Test
All One	Solution Test
Insert Delete GetRandom O(1)			Solution Test
Red-Black Tree			Solution Test
Palindrome			Solution Test
Product of the Last K Numbers	Solution Test
Iterator for Combination	Solution Test

Backtracking

Medium

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Generate Parentheses	Solution Test
Pattern Matching	Solution Test

Hashtable

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Binary Subarrays With Sum	Solution Test
Rabbits in Forest	Solution Test
Longest String Chain	Solution Test
Sort Characters By Frequency	Solution Test
Sparse Matrix Multiplication	Solution Test

Union and Find

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Friend Circles	Solution Test

Double Pointer

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Long Pressed Name	Solution Test
Fruit Into Baskets	Solution Test

Range

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Smallest Range			Solution Test

BFS/DFS

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
Super Palindromes	Solution Test
WordLadder	Solution Test
Open the Lock	Solution Test

Design

Problem List	Java	Python	C++	Swift	JavaScript	Scala	Go
PackageManager	Solution
Amazon 1 Amazon 2	Solution Test		Solution Test

Advanced algorithm

Design Pattern

Pattern

Creational

Pattern List	Solution 1	Solution 2	Solution 3	Solution 4
Abstract Factory
Builder
Singleton	Early Initialization	Lazy Initialization	Class holder	Enum

Structural

Pattern List	Solution 1	Solution 2	Solution 3	Solution 4
Adapter
Bridge
Composite
Decrorator
Facade
FlyWeight	Generic
Proxy

Behavioral

Pattern List	Solution 1	Solution 2	Solution 3	Solution 4
Chain of Responsibility
Command
Iterpreter
Iterator
Mediator
Memento
Observer(Listener)
State
Strategy
Visitor

Anti-Pattern

Multiple Thread Programming

System Design Practice

Concept

Proxies

Load Balancing

Caching

• Distributed Cache
• MemCached
• Redis

Sharding and Data Partition

-[Horizontal partitioning vs Vertical Partitioning]

Deal with Sharing Problem

• [Joins and Denormalization]
• [Referential integrity]
• [Rebalancing]

Consistent Hashing

• Princeton Essay(Original)
• Stanford essay

Copysets

• https://web.stanford.edu/~skatti/pubs/usenix13-copysets.pdf

CAP Theorem(Consistency,Availability,Partition Tolerance)

• WIKI CAP_theorem

Storage

• LSM vs B-Tree Link1

Vector Clock

• Why Vector Clock is easy
• Why Cassandra doesn’t need vector clocks

Protocol

• Raft Link1
• Paxos Link1

Event Update

-[Long-Polling(pull) vs WebSockets vs Server-Sent Events(push)]

Practice

• TinyURL
• Web Crawler
• Twitter
• Search Engine
• Messenger
• Dropbox

SQL

Question	My SQL	Oracle	SQL Server
Combine Two Tables	Solution
Second Highest Salary	Solution
Rank Scores	Solution
Employees Earning More Than Their Managers	Solution
Duplicate Emails	Solution
Customers Who Never Order	Solution
Rising Temperature	Solution