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Ingy döt Net 2023-07-01 11:58:00 -04:00
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Task/Levenshtein-distance/Prolog/levenshtein-distance.pro Normal file
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levenshtein(S, T, R) :-
length(S, M),
M1 is M+1,
length(T, N),
N1 is N+1,
length(Lev, N1),
maplist(init(M1), Lev),
numlist(0, N, LN),
maplist(init_n, LN, Lev),
nth0(0, Lev, Lev0),
numlist(0, M, Lev0),
% compute_levenshtein distance
numlist(1, N, LN1),
maplist(work_on_T(Lev, S), LN1, T),
last(Lev, LevLast),
last(LevLast, R).
work_on_T(Lev, S, J, TJ) :-
length(S, M),
numlist(1, M, LM),
maplist(work_on_S(Lev, J, TJ), LM, S).
work_on_S(Lev, J, C, I, C) :-
% same char
!,
I1 is I-1, J1 is J-1,
nth0(J1, Lev, LevJ1),
nth0(I1, LevJ1, V),
nth0(J, Lev, LevJ),
nth0(I, LevJ, V).
work_on_S(Lev, J, _C1, I, _C2) :-
I1 is I-1, J1 is J - 1,
% compute the value for deletion
nth0(J, Lev, LevJ),
nth0(I1, LevJ, VD0),
VD is VD0 + 1,
% compute the value for insertion
nth0(J1, Lev, LevJ1),
nth0(I, LevJ1, VI0),
VI is VI0 + 1,
% compute the value for substitution
nth0(I1, LevJ1, VS0),
VS is VS0 + 1,
% set the minimum value to cell(I,J)
sort([VD, VI, VS], [V|_]),
nth0(I, LevJ, V).
init(Len, C) :-
length(C, Len).
init_n(N, L) :-
nth0(0, L, N).