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fix(railfence): size zigzag by characters, not bytes - #1037
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The decoder took text.len() (bytes) positions from the zigzag but zipped them with chars(), so any input with a multi-byte character was assigned the wrong rail positions and decoded to garbled text.
Keep master's counting-sort decoder, sized by characters as this PR intends, and update the reference test to the character-based version.
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Problem
Rail fence decoding of text containing multi-byte characters returns wrongly ordered output. E.g.
railfence_decoder("ÄCEBDF", 2, 0)gaveÄDCFEBinstead ofÄBCDEF.Cause
railfence_decodergeneratedtext.len()zigzag positions (bytes) but pairs them withtext.chars(). The extra positions shift which characters land on which rail.Fix
Use
text.chars().count().Testing
Added
railfence_decoder_counts_chars_not_bytes; it fails before the change and passes after.cargo test --lib railfencepasses.