RosettaCodeData/Task/Longest-common-subsequence/Picat/longest-common-subsequence-2.picat
2023-07-01 13:44:08 -04:00

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table
lcs_rule(A, B) = "", (A == ""; B == "") => true.
lcs_rule(A, B) = [A[1]] ++ lcs_rule(butfirst(A), butfirst(B)), A[1] == B[1] => true.
lcs_rule(A, B) = longest(lcs_rule(butfirst(A), B), lcs_rule(A, butfirst(B))) => true.
% Return the longest string of A and B
longest(A, B) = cond(A.length > B.length, A, B).
% butfirst (everything except first element)
butfirst(A) = [A[I] : I in 2..A.length].