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What is LZW compression? Explain with example.

Decoding the Magic of LZW Compression: A Data Compression Deep Dive

What is LZW Compression?

  • Lempel-Ziv-Welch (LZW) is a lossless data compression algorithm.
  • It works by replacing repeating sequences of data with shorter codes.
  • It's widely used in GIF image format and other applications.
  • Highly effective for data with repeating patterns.

How LZW Compression Works: A Step-by-Step Guide

  • Starts with a dictionary containing single characters.
  • Reads the input data character by character.
  • Concatenates characters to form strings.
  • When a string is not found, it's added to the dictionary with a new code.
  • The code for the longest matching string is written to the output.
  • This process continues until the entire input is processed.

LZW Compression Example:

  • Initial Dictionary: {'A': 1, 'B': 2, 'C': 3}
  • Input String: "ABABCABABCACC"
  • Processing:
- 'A' is encoded as 1. - 'AB' is encoded as 4 (added to dictionary). - 'ABA' is encoded as 5 (added to dictionary). - 'ABAB' is encoded as 6 (added to dictionary). - 'C' is encoded as 3. - 'ABAB' is encoded as 6. - 'CACC' is encoded as 7 (added to dictionary).
  • Compressed Output: 1, 4, 5, 6, 3, 6, 7

Decompression:

  • Uses the dictionary to reverse the encoding process.
  • Reads the codes from the compressed data.
  • Looks up the corresponding strings in the dictionary.
  • Reconstructs the original string.

Advantages of LZW Compression

  • Lossless compression—no data is lost.
  • Adaptive—the dictionary grows dynamically.
  • Relatively simple to implement.

Disadvantages of LZW Compression

  • Can be slower than some other methods.
  • Requires significant memory for the dictionary.
**Google Search Description:** Learn LZW compression: a lossless data compression algorithm explained with examples. Understand its workings, advantages, and disadvantages in data compression.
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