17 lines
689 B
Text
17 lines
689 B
Text
class BurrowsWheelerTransform{
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fcn init(chr="$"){ var special=chr; }
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fcn encode(str){
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_assert_(not str.holds(special), "String cannot contain char \"%s\"".fmt(special) );
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str=str.append(special);
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str.len().pump(List().merge,'wrap(n){ String(str[n,*],str[0,n]) })
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.pump(String,T("get",-1)); // last char of each "permutation"
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}
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fcn decode(str){
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table:=List.createLong(str.len(),""); // ("",""..), mutable
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do(str.len()){
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foreach n in (str.len()){ table[n]=str[n] + table[n] }
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table.sort();
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} // --> ("$dogwood","d$dogwoo","dogwood$",...)
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table.filter1("%s*".fmt(special).glob)[1,*]; // str[0]==$, often first element
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}
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}
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