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Abstract Vector Spaces

The Definition of a Vector Space

Subspaces

Bases and Dimension

Linear Independence, Spanning Sets, and Bases

Abstract Vector Spaces

The Definition of a Vector Space

Subspaces

Bases and Dimension

Linear Independence, Spanning Sets, and Bases

Linear Algebra Theorems & Definitions

\theta(height)

insert:

\theta(height)

delete:

\theta(height)

Worst case cost for all operations is

\theta(height) = \theta(log \space n)

Other Dictionary Implementations

Dictionary ADT

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Unordered array or linked list: θ(1)\theta(1)θ(1) insert, θ(n)\theta(n)θ(n) search and delete

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Ordered array: θ(logn)\theta(log n)θ(logn) search, θ(n)\theta(n)θ(n) insert and delete

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Binary Search Trees: θ(height)\theta(height)θ(height) search, insert, delete

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Balanced BST (AVL): θ(log n)\theta(log \space n)θ(log n) search, insert, and delete

Data Structures and Data Management

Basic Principles of Enumeration

The Essential Ideas

Lists, permutations and subsets

Multisets

Bijective Proofs

Inclusion/Exclusion

Handshaking Lemma (Degree-Sum Formula)

The average degree of a vertex in the graph G

Corollary

Bipartite Graphs

Degree

Definitions

Regular Graph

If a graph in which every vertex has degree k, for some fixed k, is called a k-regular graph (or a regular graph)

Theorems

Handshaking Lemma (Degree-Sum Formula)

\underset{v \in V(G)}{\Sigma} deg(v) = 2|E(G)|

The average degree of a vertex in the graph G

\frac{2|E(G)|}{|V(G)|}

Corollary

The number of vertices of odd degree in a graph is even.

Bipartite Graphs

Graph Theory

Dev

Guidelines

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Seperate subject from body with a blank line

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Do not end the subject liine with a period

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Capitalize the subject line and each paragraph

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Use the imperative mood in the subject line

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Wrap lines at 72 characters

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Use the body to explain what and why you have done something rather than how. 

Summary

Tips

Use type on subject line if you want:

Use bullet points on body paragraph - I prefer this

Put references on footer if you use an issue tracker:

References

Git Commit Message

신입 웹 개발자일 때 알았더라면 좋았을 기본 웹 아키텍처 개념

이 글은 미디엄의 Web Archtecture 101(https://engineering.videoblocks.com/web-architecture-101-a3224e126947) 글을 보기 쉽게 번역한 글입니다. Storyblocks라는 웹 서비스의 구성을 통해 입문자 관점에서 모던 웹 아키텍처를 설명해주고 있습니다. 모던 웹 애플리케이션 아키텍쳐 개요 위의 다이어그램은 우리 Storyblocks의 아키텍쳐를 꽤 잘 나타낸다. 당신이 경험 많은 웹 개발자가 아니라면 아마도 꽤 복잡하다고 생각할 것이다.

https://kschoi.github.io/cs/the-basic-archtecture-concepts/

Domain Name Server

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enables WWW

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changes domain name to ip address

Load Balancer

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Horizontal scaling is always better than vertical scaling

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enables horizontal scaling 

Web Application Server

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executes business logic and sends responds through HTML

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Should choose proper server language (Node.js, Ruby, PHP, Scala, Java, C#, .NET, ...) and its web MVC framework (Express for Node.js, Ruby on Rails, Play for Scala, Laravel for PHP)

Database Server

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struct, insert, find, modify, delete, and compute data

Backend Architecture

The purpose of this post is only for inspecting and enhancing my knowledge, revealing that the resources for most contents from CS246 at the University of Waterloo.

Introduction

Maximize Cohesion Minimize Coupling

Terms

Procedural vs Object-Oriented Programming

Object-Oriented Programming

What is ARC

When does ARC perform?

What is ARC

ARC stands for Automatic Reference Counting. It manages memory. Only if reference counting becomes 0, memory will be deallocated.

When does ARC perform?

When it compiles

ARC vs GC

ARC counts when it compiles, so it’s easy to predict when the instance memory will be deallocated, but that also means there is a chance that instance never deallocated in memory.

GC counts when the program runs, so it reduces performance as we need more resources to count references and in contrast to ARC it’s hard to predict when the instance will be deallocated from memory. However, we have more opportunity to deallocate memory even in complex situation and do not need to worry about such rules.

Weak Strong Unowned

Strong

Strong owns object and reference count will increase. Retain when assigned and Released when counting ends.

Weak

Weak does not own object but only have address, just like point. Although weak does do refer to some object, it can’t deallocate the object. Thus, there is no retain or therefore release. So, we don’t know when and how this memory will be used or deallocated. But once if the memory released, ARC will change this reference to nil. That means, weak object should be optional.

Delegate pattern.

iOS Interview Prep

Resume

Methodology for Interview

STAR

Resume

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언어 + 툴들은 work experience / project based

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Use Achieved X by performing Y, measured in Z format

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Your work experience is not your work summary

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soft skill을 넣고 싶은거라면 soft skill만이 표현할 수 있는 부분을 강조하라 괜히 보통 적듯이 수치적으로 넣지말고 soft skill만이 표현할 수 있는 점을 강조하라

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레쥬미 크리틱은 꼭 받자 가능하다면 실무자에게 괜히 사부가 있는게 아니다..

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단순히 tech를 나열하지 말자 

Methodology for Interview

STAR

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상황: Describe the situation

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일: Describe the task

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행동: Describe the action taken to handle the task

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결과: Share the results achieved

Interview Hack

Finance

서론

향후 쓰일 기술이 무엇이 있을까 고민을 해보자. 아래의 조건을 충족하는 기술들. 그러나 회사(주식)에 국한되지 않게 생각을 해보자. 원초적으로.

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현재 우리의 삶을 변화시킬 기술

저 문장을 조금 더 깊게 파고 들어가보자.

현재에 대해 초점을 맞추어서 고민해보자.

현재 우리의 삶이란 무엇인가?

그 삶은 어떤 기술을 바탕으로 만들어진 것인가?

그 기술은 무엇을 필요로 하는가?

변화에 초점을 두어서 고민해보자.

우리는 왜 이런 삶에 만족하지 않고 왜 더 나은 것을 바라는가?

대안책은 어떠한 기술을 필요로 하는가?

현재 우리의 삶 (동사)

Stocks Portfolio Plan

투자

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50억원 (42 milllion dollar)

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평균 시리즈 A 투자 금액: 2 ~ 15 million / 5 ~ 10 million

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평균 시리즈 B 투자 금액: 10 ~ 50 million / 11 ~ 18 million

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평균 시리즈 C 투자 금액: 20 ~ 100 million / 25 ~ 35 million

투자 전략

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50억이라는 다소 적은 투자 금액

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경기 침체 / 불확실성

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레이아웃

테마 선정 이유

회사 선정 이유

VC 투자 with Theme

Git

No Category

Posts

Abstract Vector Spaces

The Definition of a Vector Space

Subspaces

Bases and Dimension

Linear Independence, Spanning Sets, and Bases

Basic Principles of Enumeration

The Essential Ideas

Lists, permutations and subsets

Multisets

Bijective Proofs

Inclusion/Exclusion

Degree

Definitions

Regular Graph

Theorems

Handshaking Lemma (Degree-Sum Formula)

The average degree of a vertex in the graph G

Corollary

Bipartite Graphs

Guidelines

Summary

Tips

References

Introduction

Terms

Module

Cohesion (응집도)

Coupling (결합도)

Procedural vs Object-Oriented Programming

What is ARC

When does ARC perform?

ARC vs GC

Weak Strong Unowned

Strong

Weak

Resume

Methodology for Interview

STAR