Back to Compression
Run-Length Encoding (RLE)
Simple compression for repetitive data sequences
Algorithm Type
Lossless, sequence-based compression
Time Complexity
O(n) - single pass through data
Best Use Case
Images, fax transmission, simple graphics
RLE Compression Simulator
Try these examples:
RLE Algorithm Explanation
How RLE Works
1. Scan Input: Read through the input data sequentially
2. Count Runs: Count consecutive identical characters
3. Encode Runs: Replace runs with count + character (e.g., "AAA" → "3A")
4. Handle Singles: Single characters remain unchanged or use count 1
5. Output Result: Concatenate all encoded sequences
Advantages
- • Extremely simple to implement
- • Very fast compression/decompression
- • Low memory requirements
- • Perfect for repetitive data
- • Real-time compression possible
Disadvantages
- • Poor compression for diverse data
- • Can increase file size if no repetition
- • Limited to consecutive sequences
- • Not suitable for text with mixed content
- • Count field limits run length
Real-world Applications
Image Compression:
- • Fax machines (CCITT Group 3/4)
- • Simple bitmap images
- • Icons and logos
Other Uses:
- • Video compression (as preprocessing)
- • Database compression
- • Simple data streaming
📝 Exam Preparation Tips
Key Points to Remember
- • RLE works best with consecutive repeated characters
- • Format: count + character (e.g., "5A" for "AAAAA")
- • Single characters may remain unchanged
- • Can increase size if no repetition exists
- • Decompression reverses the process
Common Exam Questions
- • "Compress given string using RLE" (5 marks)
- • "Calculate compression ratio" (3 marks)
- • "When is RLE most/least effective?" (4 marks)
- • "Decompress RLE encoded data" (4 marks)
- • "Compare RLE with other algorithms" (6 marks)