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TIL
  • README
  • Git
    • Basic
    • Remote Repository
    • Log & Diff
    • Rebase&Cherri-Pick
    • git-flow
  • DevOps
    • Monolithic vs MSA
    • Jenkins ์‹œ์ž‘ํ•˜๊ธฐ
    • Airflow ์‹œ์ž‘ํ•˜๊ธฐ
    • Airflow ์‹œ์ž‘ํ•˜๊ธฐ
    • Build Tools
      • maven
  • ๊ฐœ๋ฐœ ๋ฐฉ๋ฒ•๋ก 
    • TDD
  • Spring
    • IoC
    • Is Spring Bean Thread-Safe?
    • Spring Singleton
    • Component Scan
    • Spring Annotation
    • ์˜์กด ๊ด€๊ณ„ ์ฃผ์ž…(DI)
    • Lombok ํ™œ์šฉํ•˜๊ธฐ
    • Bean ์ƒ๋ช…์ฃผ๊ธฐ์™€ ์ฝœ๋ฐฑ
    • Bean Scope
    • AOP(1) - AOP๋ž€
    • AOP(2) - Aop Proxy
    • AOP(3) - Dynamic Proxy
    • AOP(4) - AspectJ
    • POJO
    • Spring ์„œ๋น„์Šค ๊ตฌ์กฐ
    • Transaction
    • JPA๋ž€?
    • JPA Entity
    • Spring Data JPA
    • Spring Data Specification
    • Model Mapping
    • Cache
    • restTemplate
    • YAML ํŒŒ์ผ ์„ค์ •
    • Spring Boot
      • H2 DB ์„ค์ •
      • ๋‹ค์ค‘ ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค ์„ค์ •
      • Mybatis ์—ฐ๋™ํ•˜๊ธฐ
    • Spring Batch
      • Batch ์‹œ์ž‘ํ•ด๋ณด๊ธฐ
      • Batch Job Flow
      • Job
      • Step
      • Batch Scope & Job Parameter
      • JobRepository์™€ ๋ฉ”ํƒ€ํ…Œ์ด๋ธ”
      • Chunk ์ง€ํ–ฅ ํ”„๋กœ๊ทธ๋ž˜๋ฐ
      • ItemReader
      • ItemProcessor
      • ItemWriter
      • Batch Schedular
      • Job๋ณ„ Bean๋“ฑ๋กํ•˜๊ธฐ
      • Batch ๊ตฌํ˜„์‹œ ๋ฐœ์ƒํ•œ ์˜ค๋ฅ˜ ์ •๋ฆฌ
      • Spring Batch Scaling
        • Multithread Job๊ตฌํ˜„์‹œ ์ด์Šˆ์‚ฌํ•ญ
    • Spring test
      • Junit5
        • ํ…Œ์ŠคํŠธ ์ด๋ฆ„ ํ‘œ๊ธฐ
        • ํ…Œ์ŠคํŠธ ๊ทธ๋ฃน ์‚ฌ์ด์˜ ๊ด€๊ณ„
        • ํƒœ๊ทธ์™€ ํ•„ํ„ฐ๋ง
        • ๋™์  ํ…Œ์ŠคํŠธ
        • ํ…Œ์ŠคํŠธ LifeCycle
        • ํ…Œ์ŠคํŠธ ๋ฉ”์„œ๋“œ
        • ํ…Œ์ŠคํŠธ ์ˆœ์„œ
        • AssertJ
        • ํ…Œ์ŠคํŠธ ๋ณ‘๋ ฌ ์‹คํ–‰
        • AssertJ
        • Mock
      • Spring Boot Test DB ๋ถ„๋ฆฌ
      • Spring Batch Test
  • Web Application
    • Web Server & WAS
    • ๊ด€๋ จ ๊ฐœ๋… - HTTP API, HTML, CSR, SSR
    • Servlet
    • JSP
    • Cookie And Session
    • ์˜ˆ์™ธํŽ˜์ด์ง€
    • Java Bean
    • JDBC
    • Connection Pool
    • ํŒŒ์ผ ์—…๋กœ๋“œ
    • Expression Language
    • JSTL
    • FrontControllerํŒจํ„ด Command ํŒจํ„ด
    • Forwarding
    • MVC
    • ํšŒ์›๊ฐ€์ž…์˜ˆ์ œ
    • ์ฐธ๊ณ 
      • ๊ฐœ๋ฐœํ™˜๊ฒฝ์„ค์ •
  • Java+
    • SOAP/WSDL vs REST
    • WSDL์„ JAVA๋กœ ๋ณ€ํ™˜ํ•˜๊ธฐ
    • SOAP ํ†ต์‹  OPEN API๋กœ ๊ฐœ๋ฐœํ•ด๋ณด๊ธฐ
  • Java
    • Basic
      • ๋ณ€์ˆ˜์™€ ํƒ€์ž…
      • ์—ฐ์‚ฐ์ž
      • ์กฐ๊ฑด๋ฌธ๊ณผ ๋ฐ˜๋ณต๋ฌธ
      • ์ฐธ์กฐ ํƒ€์ž…
      • ํด๋ž˜์Šค
      • ์ƒ์†(Inheritance)
      • ์ธํ„ฐํŽ˜์ด์Šค(Interface)
      • ์ค‘์ฒฉ ํด๋ž˜์Šค์™€ ์ค‘์ฒฉ ์ธํ„ฐํŽ˜์ด์Šค
      • ์˜ˆ์™ธ ์ฒ˜๋ฆฌ
      • API - Object, System, Class, Math, Wrapper
      • API - String, StringBuffer, StringBuilder
      • Thread
      • Generic
      • Lambda
      • Collection - List, Set
      • Collection - Map
      • Collection - Tree
      • Collection - Stack, Queue
      • Stream
      • Reflection
      • ์ •๊ทœํ‘œํ˜„์‹
      • GUI
      • UML
      • Serializable
    • Advanced
      • OutOfMemoryError
      • AutoValue
      • meta-annotation
        • @Retention
        • @Target
        • @Repeatable
    • Effective Java 3/E
      • ITEM 1: Static Factory Method(์ •์  ๋ฉ”์†Œ๋“œ)
      • ITEM 2: Builder Pattern
      • ITEM 3: Singleton
      • ITEM 4: Private Constructor
      • ITEM 5: Dependency Injection
      • ITEM 6: Avoid Unnecessary Object
      • ITEM 7: Eliminate Object Reference
      • ITEM 8: Avoid finalizer and cleaner
      • ITEM 9: try-with-resources
      • ITEM 10: The gerneral contract when overriding equlas
      • ITEM 11: Overriding hashCode
      • ITEM 12: overriding toString
      • ITEM 13: overriding clone judiciously
      • ITEM 14: Consider implementing comparable
      • ITEM 15: ํด๋ž˜์Šค์™€ ๋ฉค๋ฒ„์˜ ์ ‘๊ทผ์„ ์ตœ์†Œํ™”ํ•ด๋ผ
      • ITEM 16: Use Accessor methods
      • ITEM 17: ๋ณ€๊ฒฝ ๊ฐ€๋Šฅ์„ฑ์„ ์ตœ์†Œํ™”ํ•ด๋ผ(๋ถˆ๋ณ€ ํด๋ž˜์Šค)
      • ITEM 18: ์ƒ์†๋ณด๋‹จ ์ปดํฌ์ง€์…˜์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 19: ์ƒ์†์„ ๊ณ ๋ คํ•ด ์„ค๊ณ„ํ•˜๊ณ  ๋ฌธ์„œํ™”ํ•ด๋ผ
      • ITEM 20: ์ถ”์ƒ ํด๋ž˜์Šค๋ณด๋‹ค ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์šฐ์„ ํ•˜๋ผ
      • ITEM 21: ์ธํ„ฐํŽ˜์ด์Šค๋Š” ๊ตฌํ˜„ํ•˜๋Š” ์ชฝ์„ ์ƒ๊ฐํ•ด ์„ค๊ณ„ํ•ด๋ผ.
      • ITEM 22: ์ธํ„ฐํŽ˜์ด์Šค๋Š” ํƒ€์ž…์„ ์ •์˜ํ•˜๋Š” ์šฉ๋„๋กœ๋งŒ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 23: ํƒœ๊ทธ ๋‹ฌ๋ฆฐ ํด๋ž˜์Šค๋ณด๋‹ค ํด๋ž˜์Šค ๊ณ„์ธต๊ตฌ์กฐ๋ฅผ ํ™œ์šฉํ•ด๋ผ
      • ITEM 24: ๋ฉค๋ฒ„ ํด๋ž˜์Šค๋Š” ๋˜๋„๋ก static์œผ๋กœ ๊ตฌํ˜„ํ•ด๋ผ
      • ITEM 25: ํ†ฑ๋ ˆ๋ฒจ ํด๋ž˜์Šค๋Š” ํ•œ ํŒŒ์ผ์— ํ•˜๋‚˜๋งŒ ์ƒ์„ฑํ•ด๋ผ.
      • ITEM 26: Raw type์€ ์‚ฌ์šฉํ•˜์ง€ ๋งˆ๋ผ
      • ITEM 27: ๋น„๊ฒ€์‚ฌ ๊ฒฝ๊ณ ๋ฅผ ์ œ๊ฑฐํ•ด๋ผ
      • ITEM 28: ๋ฐฐ์—ด๋ณด๋‹ค๋Š” ๋ฆฌ์ŠคํŠธ๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 29: ์ด์™•์ด๋ฉด ์ œ๋„ค๋ฆญ ํƒ€์ž…์œผ๋กœ ๋งŒ๋“ค์–ด๋ผ
      • ITEM 30: ์ด์™•์ด๋ฉด ์ œ๋„ค๋ฆญ ๋ฉ”์„œ๋“œ๋กœ ๋งŒ๋“ค์–ด๋ผ
      • ITEM 31 : ํ•œ์ •์  ์™€์ผ๋“œ์นด๋“œ๋ฅผ ์‚ฌ์šฉํ•ด API ์œ ์—ฐ์„ฑ์„ ๋†’์—ฌ๋ผ
      • ITEM 32: ์ œ๋„ค๋ฆญ๊ณผ ๊ฐ€๋ณ€์ธ์ˆ˜๋ฅผ ํ•จ๊ป˜ ์“ธ ๋•Œ๋Š” ์‹ ์ค‘ํ•ด๋ผ
      • ITEM 33: ํƒ€์ž… ์•ˆ์ „ ์ด์ข… ์ปจํ…Œ์ด๋„ˆ๋ฅผ ๊ณ ๋ คํ•ด๋ผ
      • ITEM 34: int ์ƒ์ˆ˜ ๋Œ€์‹  ์—ด๊ฑฐ ํƒ€์ž…์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 35: ordinal ๋ฉ”์„œ๋“œ ๋Œ€์‹  ์ธ์Šคํ„ด์Šค ํ•„๋“œ๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 36: ๋น„ํŠธ ํ•„๋“œ ๋Œ€์‹  EnumSet์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 37: ordinal ์ธ๋ฑ์‹ฑ ๋Œ€์‹  EnumMap์„ ์‚ฌ์šฉํ•ด๋ผ
      • TEM 38 : ํ™•์žฅํ•  ์ˆ˜ ์žˆ๋Š” ์—ด๊ฑฐํƒ€์ž…์ด ํ•„์š”ํ•˜๋ฉด ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 39: ๋ช…๋ช… ํŒจํ„ด๋ณด๋‹ค ์• ๋„ˆํ…Œ์ด์…˜์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 40: @Override ์–ด๋…ธํ…Œ์ด์…˜์„ ์ผ๊ด€๋˜๊ฒŒ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 41: ์ •์˜ํ•˜๋ ค๋Š” ๊ฒƒ์ด ํƒ€์ž…์ด๋ผ๋ฉด ๋งˆ์ปค ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 42: ์ต๋ช… ํด๋ž˜์Šค๋ณด๋‹ค๋Š” ๋žŒ๋‹ค๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 43: ๋žŒ๋‹ค๋ณด๋‹ค๋Š” ๋ฉ”์„œ๋“œ ์ฐธ์กฐ๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 44: ํ‘œ์ค€ ํ•จ์ˆ˜ํ˜• ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 45: ์ŠคํŠธ๋ฆผ์€ ์ฃผ์˜ํ•ด์„œ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 46: ์ŠคํŠธ๋ฆผ์—์„œ ๋ถ€์ž‘์šฉ ์—†๋Š” ํ•จ์ˆ˜๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 47: ๋ฐ˜ํ™˜ ํƒ€์ž…์œผ๋กœ๋Š” ์ŠคํŠธ๋ฆผ๋ณด๋‹ค ์ปฌ๋ ‰์…˜์ด ๋‚ซ๋‹ค.
      • ITEM 48: ์ŠคํŠธ๋ฆผ ๋ณ‘๋ ฌํ™”๋Š” ์ฃผ์˜ํ•ด์„œ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 49: ๋งค๊ฐœ๋ณ€์ˆ˜๊ฐ€ ์œ ํšจํ•œ์ง€ ๊ฒ€์‚ฌํ•ด๋ผ
      • ITEM 50: ์ ์‹œ์— ๋ฐฉ์–ด์  ๋ณต์‚ฌ๋ณธ์„ ๋งŒ๋“ค์–ด๋ผ
      • ITEM 51: ๋ฉ”์„œ๋“œ ์‹œ๊ทธ๋‹ˆ์ฒ˜๋ฅผ ์‹ ์ค‘ํžˆ ์„ค๊ณ„ํ•ด๋ผ
      • ITEM 52: ๋‹ค์ค‘์ •์˜๋Š” ์‹ ์ค‘ํžˆ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 53: ๊ฐ€๋ณ€์ธ์ˆ˜๋Š” ์‹ ์ค‘ํžˆ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 54: null์ด ์•„๋‹Œ, ๋นˆ ์ปฌ๋ ‰์…˜์ด๋‚˜ ๋ฐฐ์—ด์„ ๋ฐ˜ํ™˜ํ•ด๋ผ
      • ITEM 55: Optional ๋ฐ˜ํ™˜์€ ์‹ ์ค‘ํ•˜๊ฒŒ ํ•ด๋ผ
      • ITEM 56: ๊ณต๊ฐœ๋œ API ์š”์†Œ์—๋Š” ํ•ญ์ƒ ์ฃผ์„์„ ์ž‘์„ฑํ•ด๋ผ
      • ITEM 57: ์ง€์—ญ๋ณ€์ˆ˜์˜ ๋ฒ”์œ„๋ฅผ ์ตœ์†Œํ™”ํ•ด๋ผ
      • ITEM 58: ์ „ํ†ต์ ์ธ for ๋ฌธ๋ณด๋‹ค๋Š” for-each๋ฌธ์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 59: ๋ผ์ด๋ธŒ๋Ÿฌ๋ฆฌ๋ฅผ ์ตํžˆ๊ณ  ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 60: ์ •ํ™•ํ•œ ๋‹ต์ด ํ•„์š”ํ•˜๋‹ค๋ฉด float์™€ double์€ ํ”ผํ•ด๋ผ
      • ITEM 61: ๋ฐ•์‹ฑ๋œ ๊ธฐ๋ณธ ํƒ€์ž…๋ณด๋‹ค๋Š” ๊ธฐ๋ณธ ํƒ€์ž…์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 62: ๋‹ค๋ฅธ ํƒ€์ž…์ด ์ ์ ˆํ•˜๋‹ค๋ฉด ๋ฌธ์ž์—ด ์‚ฌ์šฉ์„ ํ”ผํ•ด๋ผ
      • ITEM 63: ๋ฌธ์ž์—ด ์—ฐ๊ฒฐ์€ ๋А๋ฆฌ๋‹ˆ ์ฃผ์˜ํ•ด๋ผ
      • ITEM 64: ๊ฐ์ฒด๋Š” ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์‚ฌ์šฉํ•ด ์ฐธ์กฐํ•ด๋ผ
      • ITEM 65: ๋ฆฌํ”Œ๋ ‰์…˜๋ณด๋‹ค๋Š” ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 66: ๋„ค์ดํ‹ฐ๋ธŒ ๋ฉ”์„œ๋“œ๋Š” ์‹ ์ค‘ํžˆ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 67: ์ตœ์ ํ™”๋Š” ์‹ ์ค‘ํžˆ ํ•ด๋ผ
      • ITEM 68: ์ผ๋ฐ˜์ ์œผ๋กœ ํ†ต์šฉ๋˜๋Š” ๋ช…๋ช… ๊ทœ์น™์„ ๋”ฐ๋ผ๋ผ
    • ๊ฐ์ฒด์ง€ํ–ฅ ์„ค๊ณ„ ์›์น™(SOLID)
    • ๋””์ž์ธํŒจํ„ด
      • Strategy Pattern
      • Template Method Pattern
      • Factory Method Pattern
      • Singleton
      • Delegation
      • Proxy
      • Adapter Pattern
    • ์‹ค์Šต
      • ์ธํ„ฐํŽ˜์ด์Šค ์‹ค์Šต - Vehicle
      • ์ธํ„ฐํŽ˜์ด์Šค ์‹ค์Šต - Remote
      • GUI ์‹ค์Šต - Calculator
      • GUI ์‹ค์Šต - button
      • GUI ์‹ค์Šต - lotto
      • Thread ์‹ค์Šต - ์ขŒ์„์˜ˆ์•ฝ, ๋ฉ”์„ธ์ง€๋ณด๋‚ด๊ธฐ
    • Jar vs War
  • ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค
    • KEY
    • Index
    • Transaction
    • Trigger
    • Procedure / Function
    • Package
    • ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค ๋ฐฐ์›€ํ„ฐ
      • ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค ์‹œ์Šคํ…œ
      • ๊ด€๊ณ„๋ฐ์ดํ„ฐ ๋ชจ๋ธ
      • ๊ด€๊ณ„๋Œ€์ˆ˜์™€ SQL
    • MySQL
      • Database๋ž€
      • MySQL ์‹œ์ž‘ํ•˜๊ธฐ
      • MySQL Database
      • MySQL Table
      • CRUD
      • ๊ด€๊ณ„ํ˜• ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค
      • Server์™€ Client
    • PostgreSQL
    • NoSQL
      • Install Cassandra on mac
      • Cassandra๋ž€?
      • NiFi๋ž€
  • Algorithm
    • String
    • Recursion
    • Dynamic Programming
    • Array, Struct, Pointer
    • Math
    • Sort
    • List
    • Stack
    • Queue
    • Graph
    • Tree
    • Maze
    • AVL
    • ์ด์ง„ํƒ์ƒ‰ํŠธ๋ฆฌ(Binary Search Tree)
    • DFS์™€ BFS
    • ๋‹ค์ต์ŠคํŠธ๋ผ ์•Œ๊ณ ๋ฆฌ์ฆ˜(Dijkstra's Algorithm)
    • Red-Black ํŠธ๋ฆฌ
    • A* ์•Œ๊ณ ๋ฆฌ์ฆ˜
    • Heap
    • Huffman Coding
    • Priority Queue
    • Bellman-Ford ์•Œ๊ณ ๋ฆฌ์ฆ˜
    • C++
      • Class
      • STL
        • STL pair
        • STL Container - Associate Container
        • STL Container - Sequence Container
        • STL Container - Container Adapter
  • JavaScript
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  1. Algorithm

Huffman Coding

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Last updated 4 years ago

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ํ—ˆํ”„๋งŒ ๋ถ€ํ˜ธํ™”(Huffman coding)๋Š” ๋ฌด์†์‹ค ์••์ถ•์— ์“ฐ์ด๋Š” ์—”ํŠธ๋กœํ”ผ ๋ถ€ํ˜ธํ™”์˜ ์ผ์ข…์œผ๋กœ, ๋ฐ์ดํ„ฐ ๋ฌธ์ž์˜ ๋“ฑ์žฅ ๋นˆ๋„์— ๋”ฐ๋ผ์„œ ๋‹ค๋ฅธ ๊ธธ์ด์˜ ๋ถ€ํ˜ธ๋ฅผ ์‚ฌ์šฉํ•˜๋Š” ์•Œ๊ณ ๋ฆฌ์ฆ˜์ด๋‹ค.

  • ์••์ถ•์ด๋ž€ ์—„์ฒญ๋‚˜๊ฒŒ ํฐ ๋ฌธ์ œ(๋งŽ์€ ๋น„ํŠธ๋ฅผ ํ•„์š”๋กœ ํ•˜๋Š”)์˜ ์ •๋ณด๋ฅผ ๊ณ ์Šค๋ž€ํžˆ ํ‘œํ˜„ํ•˜๋ฉด์„œ๋„ ์ „์ฒด ๋น„ํŠธ๋Ÿ‰์„ ์ค„์ผ ์ˆ˜ ์žˆ๋Š” ํšจ๊ณผ์ ์ธ ๋ถ€ํ˜ธํ™” ๊ธฐ์ˆ ์˜ ๊ณผ์ •์ด๋‹ค.

  • ๋ฌด์†์‹ค ์••์ถ•์€ ๋ฐ์ดํ„ฐ ์••์ถ•์˜ ์ผ์ข…์œผ๋กœ ์†์‹ค ์••์ถ•์˜ ๋ฐ˜๋Œ€๋ง์ด๋‹ค. ์›๋ž˜์˜ ์ •๋ณด๋ฅผ ๊ทธ๋Œ€๋กœ ๋ณด์กดํ•ด์•ผ ํ•˜๊ธฐ ๋•Œ๋ฌธ์—, ์ •๋ณด ์—”ํŠธ๋กœํ”ผ์˜ ํ•œ๊ณ„๊ฐ€ ๊ทธ๋Œ€๋กœ ๋ฐ˜์˜๋œ๋‹ค. ์—ฌ๊ธฐ์—์„œ ์ •๋ณด ์—”ํŠธ๋กœํ”ผ์˜ ํ•œ๊ณ„๋ž€ ๊ฐœ๋ณ„ ์ •๋ณด์˜ ํ™•๋ฅ ๊ฐ’์— ์˜ํ•˜์—ฌ ๊ณ„์‚ฐ๋˜๋Š” ๊ฐ’์ด ์•„๋‹Œ, ์ „์ฒด ์‹ ํ˜ธ์˜ ์ƒ๊ด€๊ด€๊ณ„๋ฅผ ๋ฐ˜์˜ํ•œ ํ•œ๊ณ„๊ฐ’์ด๋‹ค.

  • ์—”ํŠธ๋กœํ”ผ ์ธ์ฝ”๋”ฉ or ์—”ํŠธ๋กœํ”ผ ๋ถ€ํ˜ธํ™”(entropy encoding) : ์‹ฌ๋ณผ์ด ๋‚˜์˜ฌ ํ™•๋ฅ ์— ๋”ฐ๋ผ ์‹ฌ๋ณผ์„ ๋‚˜ํƒ€๋‚ด๋Š” ์ฝ”๋“œ์˜ ๊ธธ์ด๋ฅผ ๋‹ฌ๋ฆฌํ•˜๋Š” ๋ถ€ํ˜ธํ™” ๋ฐฉ๋ฒ•

    • ์—”ํŠธ๋กœํ”ผ๋Š” ๊ฐ ๊ธฐํ˜ธ๊ฐ€ ํฌํ•จํ•˜๋Š” ํ‰๊ท  ์ •๋ณด๋Ÿ‰์„ ์˜๋ฏธ

    • Shannon ๋ถ€ํ˜ธํ™” ์ด๋ก ์—์„œ๋Š” ์—”ํŠธ๋กœํ”ผ๋ฅผ ์šฐ๋ฆฌ๊ฐ€ ํ•  ์ˆ˜ ์žˆ๋Š” ์ตœ์„ ์ด๋ผ ๋งํ•œ๋‹ค.

    • ์ž์ฃผ ๋ฐœ์ƒํ•˜๋Š” ๊ธฐํ˜ธ๋ฅผ ์ฐพ์•„๋‚ด๋Š” ๋ฐ ๋ชฉ์ ์ด์žˆ๋‹ค.

  • ๊ฐ€๋ณ€ ๊ธธ์ด ๋ถ€ํ˜ธํ™”(VLC) : ๋” ์ž์ฃผ ๋ฐœ์ƒํ•˜๋Š” ๊ธฐํ˜ธ๋Š” ๋” ์ ์€ ๋น„ํŠธ๋กœ ๋ถ€ํ˜ธํ™”

    • ์ฆ‰, ์ž์ฃผ ๋ฐœ์ƒํ•˜๋Š” ๊ธฐํ˜ธ๋Š” ๋นจ๋ฆฌ ์ „์†ก๋  ์ˆ˜ ์žˆ๋Š” ์ฝ”๋“œ(์ ์€ ๋น„ํŠธ), ์ž์ฃผ ๋ฐœ์ƒํ•˜์ง€ ์•Š๋Š” ๊ฒƒ์€ ๊ธด ์ฝ”๋“œ๊ฐ€ ๋ถ€์—ฌ๋œ๋‹ค.

ํ—ˆํ”„๋งŒ ์•Œ๊ณ ๋ฆฌ์ฆ˜์˜ ๋ถ€ํ˜ธํ™” ์ˆœ์„œ๋Š” ์•„๋ž˜์—์„œ ์œ„๋กœ ์ง„ํ–‰ํ•˜๋Š” ๋ฐฉ๋ฒ•์ด๋‹ค.

์•Œ๊ณ ๋ฆฌ์ฆ˜

  1. ์ดˆ๊ธฐํ™” : ๋ชจ๋“  ๊ธฐํ˜ธ๋ฅผ ์ถœํ˜„ ๋นˆ๋„์ˆ˜์— ๋”ฐ๋ผ ๋‚˜์—ดํ•œ๋‹ค.

  2. ๋‹จ ํ•œ ๊ฐ€์ง€ ๊ธฐํ˜ธ๊ฐ€ ๋‚จ์„ ๋•Œ๊นŒ์ง€ ์•„๋ž˜ ๋‹จ๊ณ„๋ฅผ ๋ฐ˜๋ณตํ•œ๋‹ค.

    1. ๋ชฉ๋ก์œผ๋กœ๋ถ€ํ„ฐ ๊ฐ€์žฅ ๋นˆ๋„๊ฐ€ ๋‚ฎ์€ ๊ฒƒ์„ 2๊ฐœ ๊ณ ๋ฅธ๋‹ค.

    2. ํ—ˆํ”„๋งŒ์ด ๋‘ ๊ฐ€์ง€ ๊ธฐํ˜ธ๋ฅผ ๋ถ€๋ชจ ๋…ธ๋“œ๋ฅผ ๊ฐ€์ง€๋Š” ๋ถ€ํŠธ๋ฆฌ๋ฅผ ๊ตฌ์„ฑํ•˜๊ณ  ์ž์‹ ๋…ธ๋“œ๋ฅด ์ƒ์„ฑํ•œ๋‹ค.

    3. ๋ถ€๋ชจ ๋…ธ๋“œ ๋‹จ ๊ธฐํ˜ธ๋“ค์˜ ๋นˆ๋„์ˆ˜๋ฅผ ๋”ํ•˜์—ฌ ์ฃผ ๋…ธ๋“œ์— ํ• ๋‹นํ•˜๊ณ  ๋ชฉ๋ก์˜ ์ˆœ์„œ์— ๋งž๋„๋ก ๋ชฉ๋ก์— ์‚ฝ์ž…ํ•œ๋‹ค.

    4. ๋ชฉ๋ก์—์„œ ๋ถ€๋ชจ๋…ธ๋“œ์— ํฌํ•จ๋œ ๊ธฐํ˜ธ๋ฅผ ์ œ๊ฑฐํ•œ๋‹ค.

  3. ๋ฃจํŠธ๋…ธ๋“œ๋กœ๋ถ€ํ„ฐ์˜ ๊ฒฝ๋กœ์—์„œ ๊ฐ ๊ฐ€์ง€์— ์ฝ”๋“œ์›Œ๋“œ๋ฅผ ๋ถ€์—ฌํ•œ๋‹ค.

ํ—ˆํ”„๋งŒ ์•Œ๊ณ ๋ฆฌ์ฆ˜์€ ์ž…๋ ฅ ๊ธฐํ˜ธ๋ฅผ ๋ฆฌํ”„ ๋…ธ๋“œ๋กœ ํ•˜๋Š” ์ด์ง„ ํŠธ๋ฆฌ๋ฅผ ๋งŒ๋“ค์–ด์„œ ์ ‘๋‘ ๋ถ€ํ˜ธ๋ฅผ ๋งŒ๋“ค์–ด ๋‚ด๋Š” ์•Œ๊ณ ๋ฆฌ์ฆ˜์ด๋‹ค.

๊ตฌํ˜„

Huffman ์•Œ๊ณ ๋ฆฌ์ฆ˜์€ ์ตœ์†Œ๋นˆ๋„ ์ˆ˜๋ฅผ ์ถœ๋ ฅํ•˜๊ธฐ ์œ„ํ•ด์„œ ์šฐ์„  ์ˆœ์œ„ ํ๋ฅผ ํ•„์š”๋กœํ•œ๋‹ค. ์ตœ์†Œํž™์„ ์‚ฌ์šฉํ•ด์„œ ๊ตฌํ˜„ํ•ด๋ณด์•˜๋‹ค.

๊ตฌ์กฐ์ฒด

// ๊ธฐ๋ณธ์ ์œผ๋กœ ๋…ธ๋“œ๋Š” data์ •๋ณด์™€ ๋นˆ๋„์ˆ˜๋Š” ์Œ์ˆ˜๊ฐ€์•„๋‹Œ int๊ฐ’์„ ๊ฐ–๋Š”๋‹ค.
// ํ—ˆํ”„๋งŒ์€ ์ด์ง„ํŠธ๋ฆฌ ๊ตฌ์กฐ์ด๋ฏ€๋กœ left์™€ right์˜ ํฌ์ธํ„ฐ๋ฅผ ๊ฐ–๊ณ ์žˆ๋‹ค.
typedef struct node{
    char data;
    unsigned int frequency;
    struct node * left, *right;
}Node;

// heap๋Š” heap์˜ ํฌ๊ธฐ, node array๋ฅผ ๊ฐ–๊ณ ์žˆ๋‹ค.
// capacity๋Š” ๋ฐฐ์—ด์˜ ํฌ๊ธฐ๋ฅผ ๋งํ•œ๋‹ค.
typedef struct heap{
    unsigned int size;
    unsigned int capacity;
    Node ** array;
}Heap;

new_node

Node * new_node(char data, unsigned freq){
    Node * new = (Node*)malloc(sizeof(Node));

    new->data=data;
    new->frequency=freq;
    new->left=new->right=NULL;

    return new;
}

Heap ์ดˆ๊ธฐํ™”

Heap * init(unsigned capacity){
    Heap * heap = (Heap*)malloc(sizeof(Heap));

    // ํ˜„์žฌ heap์˜ ํฌ๊ธฐ๋Š” 0์ด๋‹ค.
    heap->size=0;
    heap->capacity=capacity;
    // ๋ฐฐ์—ด์˜ ํฌ๊ธฐ ๋งŒํผ ๊ณต๊ฐ„์„ ํ• ๋‹นํ•ด์ค€๋‹ค.
    heap->array = (Node**)malloc(heap->capacity*sizeof(Node*));

    return heap;
}

heapify

๋‘ ๊ฐœ์˜ subtree๊ฐ€ min heap์ผ๋•Œ root์— ์ถ”๊ฐ€๋œ ๋…ธ๋“œ๋ฅผ ํฌํ•จํ•œ ์ „์ฒด๊ฐ€ heap์˜ ์กฐ๊ฑด์„ ๋งŒ์กฑํ•˜๋„๋ก ๊ฐ ๋…ธ๋“œ์˜ ์œ„์น˜๋ฅผ ์กฐ์ •

void swap_node(Node ** a, Node ** b){
    Node * tmp = *a;
    *a = *b;
    *b = tmp;
}

// heapify : ๋‘ ๊ฐœ์˜ subtree๊ฐ€ min heap์ผ๋•Œ root์— ์ถ”๊ฐ€๋œ ๋…ธ๋“œ๋ฅผ ํฌํ•จํ•œ ์ „์ฒด๊ฐ€
// heap์„ ๋งŒ์กฑํ•˜๋„๋ก ๊ฐ ๋…ธ๋“œ์˜ ์œ„์น˜๋ฅผ ์กฐ์ •
void heapify(Heap * h, int i){
    int min = i;
    int left = 2*i +1;    // ์™ผ์ชฝ ์ž์‹๋…ธ๋“œ
    int right = 2*i+2;    // ์˜ค๋ฅธ์ชฝ ์ž์‹๋…ธ๋“œ

    // ์™ผ์ชฝ ์ž์‹ ๋…ธ๋“œ์˜ ์ธ๋ฑ์Šค๊ฐ€ heap์˜ ํฌ๊ธฐ๋ณด๋‹ค ์ž‘๊ณ 
    // frequency๊ฐ’์ด ์ตœ์†Œ๊ฐ’์˜ frequency๋ณด๋‹ค ์ž‘์œผ๋ฉด ์ตœ์†Œ๊ฐ’์„ left๋กœ ๋ณ€๊ฒฝ
    if(left < h->size && h->array[left]->frequency < h->array[min]->frequency)min=left;
    // ์˜ค๋ฅธ์ชฝ ์ž์‹๋…ธ๋“œ๋„ ๋งˆ์ฐฌ๊ฐ€์ง€
    if(right < h->size && h->array[right]->frequency < h->array[min]->frequency)min=right;
    // ๋งŒ์•ฝ ์ตœ์†Œ๊ฐ’์ด i์™€ ๋‹ค๋ฅด๋‹ค๋ฉด ๋…ธ๋“œ์œ„์น˜๋ฅผ ๋ณ€๊ฒฝํ•ด์ค€๋‹ค.
    if(min!=i){
        swap_node(&h->array[min], &h->array[i]);
        heapify(h,min);
    }
}

delete

Node * delete(Heap * h){
    Node * tmp = h->array[0];
    h->array[0]=h->array[--h->size];
    heapify(h, 0);
    return tmp;
}

insert

void insert(Heap * h, Node * node){
    int p; //ํ˜„์žฌ ์œ„์น˜ ์ €์žฅ

    // ๋งˆ์ง€๋ง‰ ์œ„์น˜์— ์ถ”๊ฐ€
    p=++h->size-1;;

    // ์œ„์น˜ ์กฐ์ •
    while(node->frequency < h->array[(p-1)/2]->frequency){
        h->array[p] = h->array[(p-1)/2];
        p=(p-1)/2;
    }
    h->array[p]=node;
}

heap ์ƒ์„ฑ

void build_heap(Heap * h){
    int n = h->size-1;
    int i;
    for(i=(n-1)/2;i>=0;i--)
        heapify(h, i);
}

Heap * create_heap(char data[], int freq[],int size){
    //์ดˆ๊ธฐํ™”ํ•ด์„œ ์ƒ์„ฑํ•œ๋‹ค.
    Heap * heap = init(size);

    // ๋นˆ๋„์ˆ˜์™€ ๋ฐ์ดํ„ฐ๊ฐ’์„ ๋„ฃ์€ ๋…ธ๋“œ๋ฅผ ์ƒ์„ฑํ•ด์ค€๋‹ค.
    for(int i=0;i<size;i++)
        heap->array[i]=new_node(data[i], freq[i]);

    heap->size = size;
    build_heap(heap);
    return heap;
}

์ถœ๋ ฅ

//๋ฐฐ์—ด ์›์†Œ ๊ฐ’ ์ถœ๋ ฅ
void print(int arr[],int n){
    for(int i=0;i<n;i++)
        printf("%d",arr[i]);
    printf("\n");
}
int is_leaf(Node * root){
    return !(root->left) && !(root->right);   
}
// ์ตœ์ข… ์ฝ”๋“œ ์ถœ๋ ฅ
void print_code(Node * root, int arr[], int top){
    // ์™ผ์ชฝ ์ž์‹๋…ธ๋“œ(๊ฐ€์ง€)๋Š” 0์ €์žฅ
    if(root->left){
        arr[top]=0;
        print_code(root->left, arr,top+1);
    }
    // ์˜ค๋ฅธ์ชฝ ์ž์‹๋…ธ๋“œ(๊ฐ€์ง€)๋Š” 1์ €์žฅ
    if(root->right){
        arr[top]=1;
        print_code(root->right, arr,top+1);
    }
    // ๋‹จ๋ง๋…ธ๋“œ๋ฉด ์ฝ”๋“œ ์ถœ๋ ฅ
    if(is_leaf(root)){
        printf("%c: ",root->data);
        print(arr, top);
    }
}

Huffman ์ƒ์„ฑ

// heap์˜ ํฌ๊ธฐ๊ฐ€ 1์ธ์ง€ ์•„๋‹Œ์ง€ ๊ฒ€์‚ฌ
int is_one(Heap * h){
    return (h->size==1);
}
Node * build_huffman(char data[],int freq[], int size){
    Node * left, *right, *top;

    Heap * heap = create_heap(data, freq, size);

    while(!is_one(heap)){
        left = delete(heap);
        right = delete(heap);

        top = new_node('$',left->frequency+right->frequency);
        top->left=left;
        top->right= right;

        insert(heap, top);
    }
    return delete(heap);
}


void huffman(char data[],int freq[],int size){
    Node * root = build_huffman(data, freq, size);

    int arr[MAX],top=0;

    print_code(root, arr,top);
}

Main

int main(){
    char arr[] = { 'a', 'b', 'c', 'd', 'e', 'f' };
    int freq[] = { 5, 9, 12, 13, 16, 45 };

    int size = sizeof(arr) / sizeof(arr[0]);

    huffman(arr, freq, size);   
}

๊ฒฐ๊ณผ

f: 0
c: 100
d: 101
a: 1100
b: 1101
e: 111

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