3/25/13 CS200 Algorithms and Data Structures Colorado State - - PDF document

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CS200 Algorithms and Data Structures Colorado State University

PA3: Com

• mpres

essing Data using Hu Huffm ffman Cod

• ding

Sangmi Pallickara

CS200 Algorithms and Data Structures Colorado State University 3/25/13 Samgmi Lee Pallickara 2 CS200 Algorithms and Data Structures Colorado State University

Com

• mpres

essing Data using Hu Huffm ffman Cod

• ding
• Take String input
• Generate compressed bits

CS200 Algorithms and Data Structures Colorado State University

Hu Huffm ffman cod

• ding?
• Uses the symbols and their frequencies
• Constructs rooted binary tree

– Symbols are stored in the leaves

• Example:
• AEMMMEEKKMAABBBEEEEGGGMMMGGK

MGKKKKKMMMMAKKKKMEGGGKKKKKKBB EEEEMGGGMMMABBMMABBBMMMMGGGM MMMMMMKKKMMMAAMM

CS200 Algorithms and Data Structures Colorado State University

Crea eate e a Fr Freq equen ency table e

Character ¡ Frequency ¡ Huffman ¡code ¡

A ¡ 8 ¡ B ¡ 10 ¡ E ¡ 12 ¡ G ¡ 15 ¡ K ¡ 20 ¡ M ¡ 35 ¡

CS200 Algorithms and Data Structures Colorado State University

Start fr from

• m a For

Fores est of

• f Trees

ees

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CS200 Algorithms and Data Structures Colorado State University CS200 Algorithms and Data Structures Colorado State University

Gen ener erate e Hu Huffm ffman cod

• de

e

Character ¡ Frequency ¡ Huffman ¡code ¡

A ¡ 8 ¡ 111 ¡ B ¡ 10 ¡ 110 ¡ E ¡ 12 ¡ 011 ¡ G ¡ 15 ¡ 010 ¡ K ¡ 20 ¡ 10 ¡ M ¡ 35 ¡ 00 ¡

CS200 Algorithms and Data Structures Colorado State University

Now

• w, en

encod

• de

e you

• ur string
• AEMMMEEKKMAABBBEEEEGGGMMMGGK

MGKKKKKMMMMAKKKKMEGGGKKKKKKBB EEEEMGGGMMMABBMMABBBMMMMGGGM MMMMMMKKKMMMAAMM 

• 111(A)
• 011(E)
• 00(M)
• …

CS200 Algorithms and Data Structures Colorado State University

Dec ecod

• de

e the e string

• If your encoded bit is 11100011 and you have

the Huffman Tree,

CS200 Algorithms and Data Structures Colorado State University

Exer ercise e

• Build a Huffman Frequency Table for,

“Colorado” Assume that each of the symbols are Java char (16-bit unicode character)

3/25/13 Samgmi Lee Pallickara 11 CS200 Algorithms and Data Structures Colorado State University

Build a Hu Huffm ffman Tree ee based ed on

• n the

e table e

3/25/13 Samgmi Lee Pallickara 12

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CS200 Algorithms and Data Structures Colorado State University

Encod

• de

e the e String

3/25/13 Samgmi Lee Pallickara 13 CS200 Algorithms and Data Structures Colorado State University

Dec ecod

• de

e it

3/25/13 Samgmi Lee Pallickara 14 CS200 Algorithms and Data Structures Colorado State University

You

• ur tes

est ou

• utput will look
• ok like,

e,

% java PA3_Test eeyjjjj ====================================== char frequency code

• e 2 10

y 1 11 j 4 0 ====================================== Encoded bit stream 1010110000 Total number of bits without Huffman coding: 112 Total number of bits with Huffman coding: 10 Decoded String: eeyjjjj

CS200 Algorithms and Data Structures Colorado State University

• Write the implementer’s name(s) on top of each
• f the source code
• Work with the same partner (unless you get an

email after this class)