Cmat←{⊑𝕨∊0‿𝕩?≍↕𝕨;0⊸∾˘⊸∾´1+(𝕨-1‿0)𝕊¨𝕩-1} # Recursive
Cmat1←{k←⌽↕d←𝕩¬𝕨⋄∾⌽{k∾˘¨∾˜`1+𝕩}⍟𝕨d↑↓1‿0⥊0} # Roger Hui