Data commit

Task/Align-columns/Ruby/align-columns.rb

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+J2justifier = {Left: :ljust, Right: :rjust, Center: :center}
+
+=begin
+Justify columns of textual tabular input where the record separator is the newline
+and the field separator is a 'dollar' character.
+justification can be Symbol; (:Left, :Right, or :Center).
+
+Return the justified output as a string
+=end
+def aligner(infile, justification = :Left)
+  fieldsbyrow = infile.map {|line| line.strip.split('$')}
+  # pad to same number of fields per record
+  maxfields = fieldsbyrow.map(&:length).max
+  fieldsbyrow.map! {|row| row + ['']*(maxfields - row.length)}
+  # calculate max fieldwidth per column
+  colwidths = fieldsbyrow.transpose.map {|column|
+    column.map(&:length).max
+  }
+  # pad fields in columns to colwidth with spaces
+  justifier = J2justifier[justification]
+  fieldsbyrow.map {|row|
+    row.zip(colwidths).map {|field, width|
+      field.send(justifier, width)
+    }.join(" ")
+  }.join("\n")
+end
+
+require 'stringio'
+
+textinfile = <<END
+Given$a$text$file$of$many$lines,$where$fields$within$a$line$
+are$delineated$by$a$single$'dollar'$character,$write$a$program
+that$aligns$each$column$of$fields$by$ensuring$that$words$in$each$
+column$are$separated$by$at$least$one$space.
+Further,$allow$for$each$word$in$a$column$to$be$either$left$
+justified,$right$justified,$or$center$justified$within$its$column.
+END
+
+for align in [:Left, :Right, :Center]
+  infile = StringIO.new(textinfile)
+  puts "\n# %s Column-aligned output:" % align
+  puts aligner(infile, align)
+end