RosettaCodeData/Task/Longest-common-subsequence/J/longest-common-subsequence-4.j

longest=: ]`[@.(>&#)
upd=:{:@[,~ ({.@[ ,&.> {:@])`({:@[ longest&.> {.@])@.(0 = #&>@{.@[)
lcs=: 0{:: [: ([: {.&> [: upd&.>/\.<"1@:,.)/ a:,.~a:,~=/{"1 a:,.<"0@[