red-black trees in Prolog.
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library/rbtrees.yap
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453
library/rbtrees.yap
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/*
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This code implements Red-Black trees as described in:
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"Introduction to Algorithms", Second Edition
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Cormen, Leiserson, Rivest, and Stein,
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MIT Press
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*/
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:- module(rbtrees,
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[new/1,
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lookup/3,
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insert/4,
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delete/3]).
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% create an empty tree.
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new(black([],[],[],[])).
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new(K,V,black(Nil,K,V,Nil)) :-
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Nil = black([],[],[],[]).
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lookup(Key, Val, black([],_,_,[])) :- !, fail.
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lookup(Key, Val, Tree) :-
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arg(Tree,2,KA),
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compare(Cmp,KA,Key,Tree),
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lookup(Cmp,Key,Val,Tree).
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lookup(<, K, V, Tree) :-
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arg(1,Tree,NTree),
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lookup(K, V, NTree).
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lookup(>, K, V, Tree) :-
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arg(4,Tree,NTree),
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lookup(K, V, NTree).
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lookup(>, K, V, Tree) :-
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arg(3,Tree,V).
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%
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% Tree insertion
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%
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% We don't use parent nodes, so we may have to fix the root.
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%
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insert(Tree0,Key,Val,Tree) :-
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insert2(Tree0,Key,Val,TreeI,_),
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fix_root(TreeI,Tree).
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%
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% make sure the root is always black.
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%
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fix_root(black(L,K,V,R),black(L,K,V,R)).
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fix_root(red(L,K,V,R),black(L,K,V,R)).
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%
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% Cormen et al present the algorithm as
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% (1) standard tree insertion;
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% (2) from the viewpoint of the newly inserted node:
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% partially fix the tree;
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% move upwards
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% until reaching the root.
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%
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% We do it a little bit different:
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%
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% (1) standard tree insertion;
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% (2) move upwards:
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% when reaching a black node;
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% if the tree below may be broken, fix it.
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% We take advantage of Prolog unification
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% to do several operations in a single go.
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%
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%
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% actual insertion
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%
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insert2(black([],[],[],[]), K, V, T, Status) :- !,
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Nil = black([],[],[],[]),
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T = red(Nil,K,V,Nil),
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Status = not_done.
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insert2(red(L,K0,V0,R), K, V, red(NL,K0,V0,R), Flag) :-
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K @< K0, !,
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insert2(L, K, V, NL, Flag).
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insert2(red(L,K0,V0,R), K, V, red(L,K0,V0,NR), Flag) :-
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insert2(R, K, V, NR, Flag).
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insert2(black(L,K0,V0,R), K, V, NT, Flag) :-
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K @< K0, !,
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insert2(L, K, V, IL, Flag0),
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fix_left(Flag0, black(IL,K0,V0,R), NT, Flag).
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insert2(black(L,K0,V0,R), K, V, NT, Flag) :-
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insert2(R, K, V, IR, Flag0),
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fix_right(Flag0, black(L,K0,V0,IR), NT, Flag).
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%
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% How to fix if we have inserted on the left
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%
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fix_left(done,T,T,done) :- !.
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fix_left(not_done,Tmp,Final,Done) :-
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fix_left(Tmp,Final,Done).
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%
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% case 1 of RB: just need to change colors.
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%
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fix_left(black(red(Al,AK,AV,red(Be,BK,BV,Ga)),KC,VC,red(De,KD,VD,Ep)),
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red(black(Al,AK,AV,red(Be,BK,BV,Ga)),KC,VC,black(De,KD,VD,Ep)),
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not_done) :- !.
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fix_left(black(red(red(Al,KA,VA,Be),KB,VB,Ga),KC,VC,red(De,KD,VD,Ep)),
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red(black(red(Al,KA,VA,Be),KB,VB,Ga),KC,VC,black(De,KD,VD,Ep)),
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not_done) :- !.
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%
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% case 2 of RB: got a knee so need to do rotations
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%
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fix_left(black(red(Al,KA,VA,red(Be,KB,VB,Ga)),KC,VC,De),
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black(red(Al,KA,VA,Be),KB,VB,red(Ga,KC,VC,De)),
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done) :- !.
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%
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% case 3 of RB: got a line
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%
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fix_left(black(red(red(Al,KA,VA,Be),KB,VB,Ga),KC,VC,De),
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black(red(Al,KA,VA,Be),KB,VB,red(Ga,KC,VC,De)),
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done) :- !.
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%
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% case 4 of RB: nothig to do
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%
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fix_left(T,T,done).
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%
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% How to fix if we have inserted on the right
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%
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fix_right(done,T,T,done) :- !.
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fix_right(not_done,Tmp,Final,Done) :-
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fix_right(Tmp,Final,Done).
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%
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% case 1 of RB: just need to change colors.
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%
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fix_right(black(red(Ep,KD,VD,De),KC,VC,red(red(Ga,KB,VB,Be),KA,VA,Al)),
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red(black(Ep,KD,VD,De),KC,VC,black(red(Ga,KB,VB,Be),KA,VA,Al)),
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not_done) :- !.
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fix_right(black(red(Ep,KD,VD,De),KC,VC,red(Ga,Ka,Va,red(Be,KB,VB,Al))),
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red(black(Ep,KD,VD,De),KC,VC,black(Ga,Ka,Va,red(Be,KB,VB,Al))),
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not_done) :- !.
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%
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% case 2 of RB: got a knee so need to do rotations
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%
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fix_right(black(De,KC,VC,red(red(Ga,KB,VB,Be),KA,VA,Al)),
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black(red(De,KC,VC,Ga),KB,VB,red(Be,KA,VA,Al)),
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done) :- !.
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%
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% case 3 of RB: got a line
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%
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fix_right(black(De,KC,VC,red(Ga,KB,VB,red(Be,KA,VA,Al))),
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black(red(De,KC,VC,Ga),KB,VB,red(Be,KA,VA,Al)),
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done) :- !.
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%
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% case 4 of RB: nothing to do.
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%
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fix_right(T,T,done).
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%
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% simplified processor
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%
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%
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pretty_print(T) :-
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pretty_print(T,6).
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pretty_print(black([],[],[],[]),_) :- !.
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pretty_print(red(L,K,_,R),D) :-
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DN is D+6,
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pretty_print(L,DN),
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format("~t~a:~d~*|~n",[r,K,D]),
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pretty_print(R,DN).
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pretty_print(black(L,K,_,R),D) :-
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DN is D+6,
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pretty_print(L,DN),
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format("~t~a:~d~*|~n",[b,K,D]),
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pretty_print(R,DN).
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delete(T, K, NT) :-
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delete(T, K, NT, _).
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%
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% I am afraid our representation is not as nice for delete
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%
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delete(red(L,K0,V0,R), K, NT, Flag) :-
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K @< K0, !,
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delete(L, K, NL, Flag0),
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fixup_left(Flag0,red(NL,K0,V0,R),NT, Flag).
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delete(red(L,K0,V0,R), K, NT, Flag) :-
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K @> K0, !,
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delete(R, K, NR, Flag0),
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fixup_right(Flag0,red(L,K0,V0,NR),NT, Flag).
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delete(red(L,_,_,R), _, OUT, Flag) :-
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% K == K0,
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delete_red_node(L,R,OUT,Flag).
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delete(black(L,K0,V0,R), K, NT, Flag) :-
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K @< K0, !,
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delete(L, K, NL, Flag0),
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fixup_left(Flag0,black(NL,K0,V0,R),NT, Flag).
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delete(black(L,K0,V0,R), K, NT, Flag) :-
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K @> K0, !,
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delete(R, K, NR, Flag0),
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fixup_right(Flag0,black(L,K0,V0,NR),NT, Flag).
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delete(black(L,_,_,R), _, OUT, Flag) :-
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% K == K0,
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delete_black_node(L,R,OUT,Flag).
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delete_red_node(L,L,L,done) :- !.
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delete_red_node(black([],[],[],[]),R,R,done) :- !.
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delete_red_node(L,black([],[],[],[]),L,done) :- !.
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delete_red_node(L,R,OUT,Done) :-
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delete_next(R,NK,NV,NR,Done0),
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fixup_right(Done0,red(L,NK,NV,NR),OUT,Done).
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delete_black_node(L,L,L,not_done) :- !.
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delete_black_node(black([],[],[],[]),red(L,K,V,R),black(L,K,V,R),done) :- !.
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delete_black_node(black([],[],[],[]),R,R,not_done) :- !.
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delete_black_node(red(L,K,V,R),black([],[],[],[]),black(L,K,V,R),done) :- !.
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delete_black_node(L,black([],[],[],[]),L,not_done) :- !.
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delete_black_node(L,R,OUT,Done) :-
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delete_next(R,NK,NV,NR,Done0),
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fixup_right(Done0,black(L,NK,NV,NR),OUT,Done).
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delete_next(red(black([],[],[],[]),K,V,R),K,V,R,done) :- !.
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delete_next(black(black([],[],[],[]),K,V,red(L1,K1,V1,R1)),
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K,V,black(L1,K1,V1,R1),done) :- !.
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delete_next(black(black([],[],[],[]),K,V,R),K,V,R,not_done) :- !.
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delete_next(red(L,K,V,R),K0,V0,OUT,Done) :-
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delete_next(L,K0,V0,NL,Done0),
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fixup_left(Done0,red(NL,K,V,R),OUT,Done).
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delete_next(black(L,K,V,R),K0,V0,OUT,Done) :-
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delete_next(L,K0,V0,NL,Done0),
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fixup_left(Done0,black(NL,K,V,R),OUT,Done).
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fixup_left(done,T,T,done).
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fixup_left(not_done,T,NT,Done) :-
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fixup2(T,NT,Done).
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%
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% case 1: x moves down, so we have to try to fix it again.
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% case 1 -> 2,3,4 -> done
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%
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fixup2(black(black(Al,KA,VA,Be),KB,VB,red(black(Ga,KC,VC,De),KD,VD,black(Ep,KE,VE,Fi))),
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black(T1,KD,VD,black(Ep,KE,VE,Fi)),done) :- !,
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fixup2(red(black(Al,KA,VA,Be),KB,VB,black(Ga,KC,VC,De)),
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T1,
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_).
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%
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% case 2: x moves up, change one to red
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%
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fixup2(red(black(Al,KA,VA,Be),KB,VB,black(black(Ga,KC,VC,De),KD,VD,black(Ep,KE,VE,Fi))),
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black(black(Al,KA,VA,Be),KB,VB,red(black(Ga,KC,VC,De),KD,VD,black(Ep,KE,VE,Fi))),done) :- !.
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fixup2(black(black(Al,KA,VA,Be),KB,VB,black(black(Ga,KC,VC,De),KD,VD,black(Ep,KE,VE,Fi))),
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black(black(Al,KA,VA,Be),KB,VB,red(black(Ga,KC,VC,De),KD,VD,black(Ep,KE,VE,Fi))),not_done) :- !.
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%
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% case 3: x stays put, shift left and do a 4
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%
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fixup2(red(black(Al,KA,VA,Be),KB,VB,black(red(Ga,KC,VC,De),KD,VD,black(Ep,KE,VE,Fi))),
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red(black(black(Al,KA,VA,Be),KB,VB,Ga),KC,VC,black(De,KD,VD,black(Ep,KE,VE,Fi))),
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done) :- !.
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fixup2(black(black(Al,KA,VA,Be),KB,VB,black(red(Ga,KC,VC,De),KD,VD,black(Ep,KE,VE,Fi))),
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black(black(black(Al,KA,VA,Be),KB,VB,Ga),KC,VC,black(De,KD,VD,black(Ep,KE,VE,Fi))),
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done) :- !.
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%
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% case 4: rotate left, get rid of red
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%
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fixup2(red(black(Al,KA,VA,Be),KB,VB,black(C,KD,VD,red(Ep,KE,VE,Fi))),
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red(black(black(Al,KA,VA,Be),KB,VB,C),KD,VD,black(Ep,KE,VE,Fi)),
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done).
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fixup2(black(black(Al,KA,VA,Be),KB,VB,black(C,KD,VD,red(Ep,KE,VE,Fi))),
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black(black(black(Al,KA,VA,Be),KB,VB,C),KD,VD,black(Ep,KE,VE,Fi)),
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done).
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fixup_right(done,T,T,done).
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fixup_right(not_done,T,NT,Done) :-
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fixup3(T,NT,Done).
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%
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% case 1: x moves down, so we have to try to fix it again.
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% case 1 -> 2,3,4 -> done
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%
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fixup3(black(red(black(Fi,KE,VE,Ep),KD,VD,black(De,KC,VC,Ga)),KB,VB,black(Be,KA,VA,Al)),
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black(black(Fi,KE,VE,Ep),KD,VD,T1),done) :- !,
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fixup3(red(black(De,KC,VC,Ga),KB,VB,black(Be,KA,VA,Al)),T1,_).
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%
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% case 2: x moves up, change one to red
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%
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fixup3(red(black(black(Fi,KE,VE,Ep),KD,VD,black(De,KC,VC,Ga)),KB,VB,black(Be,KA,VA,Al)),
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black(red(black(Fi,KE,VE,Ep),KD,VD,black(De,KC,VC,Ga)),KB,VB,black(Be,KA,VA,Al)),
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done) :- !.
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fixup3(black(black(black(Fi,KE,VE,Ep),KD,VD,black(De,KC,VC,Ga)),KB,VB,black(Be,KA,VA,Al)),
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black(red(black(Fi,KE,VE,Ep),KD,VD,black(De,KC,VC,Ga)),KB,VB,black(Be,KA,VA,Al)),
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not_done):- !.
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%
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% case 3: x stays put, shift left and do a 4
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%
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fixup3(red(black(black(Fi,KE,VE,Ep),KD,VD,red(De,KC,VC,Ga)),KB,VB,black(Be,KA,VA,Al)),
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red(black(black(Fi,KE,VE,Ep),KD,VD,De),KC,VC,black(Ga,KB,VB,black(Be,KA,VA,Al))),
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done) :- !.
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fixup3(black(black(black(Fi,KE,VE,Ep),KD,VD,red(De,KC,VC,Ga)),KB,VB,black(Be,KA,VA,Al)),
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black(black(black(Fi,KE,VE,Ep),KD,VD,De),KC,VC,black(Ga,KB,VB,black(Be,KA,VA,Al))),
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done) :- !.
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%
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% case 4: rotate right, get rid of red
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%
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fixup3(red(black(red(Fi,KE,VE,Ep),KD,VD,C),KB,VB,black(Be,KA,VA,Al)),
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red(black(Fi,KE,VE,Ep),KD,VD,black(C,KB,VB,black(Be,KA,VA,Al))),
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done).
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fixup3(black(black(red(Fi,KE,VE,Ep),KD,VD,C),KB,VB,black(Be,KA,VA,Al)),
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black(black(Fi,KE,VE,Ep),KD,VD,black(C,KB,VB,black(Be,KA,VA,Al))),
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done).
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%
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% This code checks if a tree is ordered and a rbtree
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%
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%
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rbtree(black([],[],[],[])) :- !.
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rbtree(T) :-
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catch(rbtree1(T),msg(S,Args),format(S,Args)).
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rbtree1(black(L,K,_,R)) :-
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find_path_blacks(L, 0, Bls),
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check_rbtree(L,-1000000,K,Bls),
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check_rbtree(R,K,1000000,Bls).
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rbtree1(red(_,_,_,_)) :-
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throw(msg("root should be black",[])).
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find_path_blacks(black([],[],[],[]), Bls, Bls) :- !.
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find_path_blacks(black(L,_,_,_), Bls0, Bls) :-
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Bls1 is Bls0+1,
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find_path_blacks(L, Bls1, Bls).
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find_path_blacks(red(L,_,_,_), Bls0, Bls) :-
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find_path_blacks(L, Bls0, Bls).
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check_rbtree(black([],[],[],[]),Min,Max,Bls0) :- !,
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check_height(Bls0,Min,Max).
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check_rbtree(red(L,K,_,R),Min,Max,Bls) :-
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check_val(K,Min,Max),
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check_red_child(L),
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check_red_child(R),
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check_rbtree(L,Min,K,Bls),
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check_rbtree(R,K,Max,Bls).
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check_rbtree(black(L,K,_,R),Min,Max,Bls0) :-
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check_val(K,Min,Max),
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Bls is Bls0-1,
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check_rbtree(L,Min,K,Bls),
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check_rbtree(R,K,Max,Bls).
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check_height(0,_,_) :- !.
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check_height(Bls0,Min,Max) :-
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throw(msg("Unbalance ~d between ~w and ~w~n",[Bls0,Min,Max])).
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check_val(K, Min, Max) :- K > Min, K < Max, !.
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check_val(K, Min, Max) :-
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throw(msg("not ordered: ~w not between ~w and ~w~n",[K,Min,Max])).
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check_red_child(black(_,_,_,_)).
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check_red_child(red(_,K,_,_)) :-
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throw(msg("must be red: ~w~n",[K])).
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%count(1,16,X), format("deleting ~d~n",[X]), new(1,a,T0), insert(T0,2,b,T1), insert(T1,3,c,T2), insert(T2,4,c,T3), insert(T3,5,c,T4), insert(T4,6,c,T5), insert(T5,7,c,T6), insert(T6,8,c,T7), insert(T7,9,c,T8), insert(T8,10,c,T9),insert(T9,11,c,T10), insert(T10,12,c,T11),insert(T11,13,c,T12),insert(T12,14,c,T13),insert(T13,15,c,T14), insert(T14,16,c,T15),delete(T15,X,T16),pretty_print(T16),rbtree(T16),fail.
|
||||
|
||||
% count(1,16,X0), X is -X0, format("deleting ~d~n",[X]), new(-1,a,T0), insert(T0,-2,b,T1), insert(T1,-3,c,T2), insert(T2,-4,c,T3), insert(T3,-5,c,T4), insert(T4,-6,c,T5), insert(T5,-7,c,T6), insert(T6,-8,c,T7), insert(T7,-9,c,T8), insert(T8,-10,c,T9),insert(T9,-11,c,T10), insert(T10,-12,c,T11),insert(T11,-13,c,T12),insert(T12,-14,c,T13),insert(T13,-15,c,T14), insert(T14,-16,c,T15),delete(T15,X,T16),pretty_print(T16),rbtree(T16),fail.
|
||||
|
||||
count(I,_,I).
|
||||
count(I,M,L) :-
|
||||
I < M, I1 is I+1, count(I1,M,L).
|
||||
|
||||
test_pos :-
|
||||
new(1,a,T0),
|
||||
N = 10000,
|
||||
build_ptree(2,N,T0,T),
|
||||
% pretty_print(T),
|
||||
rbtree(T),
|
||||
clean_tree(1,N,T,_),
|
||||
bclean_tree(N,1,T,_),
|
||||
count(1,N,X), ( delete(T,X,TF) -> true ; abort ),
|
||||
% pretty_print(TF),
|
||||
rbtree(TF),
|
||||
format("done ~d~n",[X]),
|
||||
fail.
|
||||
test_pos.
|
||||
|
||||
build_ptree(X,X,T0,TF) :- !,
|
||||
insert(T0,X,X,TF).
|
||||
build_ptree(X1,X,T0,TF) :-
|
||||
insert(T0,X1,X1,TI),
|
||||
X2 is X1+1,
|
||||
build_ptree(X2,X,TI,TF).
|
||||
|
||||
|
||||
clean_tree(X,X,T0,TF) :- !,
|
||||
format("cleaning ~d~n", [X]),
|
||||
delete(T0,X,TF),
|
||||
( rbtree(TF) -> true ; abort).
|
||||
clean_tree(X1,X,T0,TF) :-
|
||||
format("cleaning ~d~n", [X1]),
|
||||
delete(T0,X1,TI),
|
||||
X2 is X1+1,
|
||||
( rbtree(TI) -> true ; abort),
|
||||
clean_tree(X2,X,TI,TF).
|
||||
|
||||
bclean_tree(X,X,T0,TF) :- !,
|
||||
format("cleaning ~d~n", [X]),
|
||||
delete(T0,X,TF),
|
||||
( rbtree(TF) -> true ; abort).
|
||||
bclean_tree(X1,X,T0,TF) :-
|
||||
format("cleaning ~d~n", [X1]),
|
||||
delete(T0,X1,TI),
|
||||
X2 is X1-1,
|
||||
( rbtree(TI) -> true ; abort),
|
||||
bclean_tree(X2,X,TI,TF).
|
||||
tree(X2,X,TI,TF).
|
||||
|
||||
|
||||
|
||||
test_neg :-
|
||||
Size = 10000,
|
||||
new(-1,a,T0),
|
||||
build_ntree(2,Size,T0,T),
|
||||
% pretty_print(T),
|
||||
rbtree(T),
|
||||
clean_tree(1,Size,T,_),
|
||||
bclean_tree(Size,1,T,_),
|
||||
count(1,Size,X), NX is -X, ( delete(T,NX,TF) -> true ; abort ),
|
||||
% pretty_print(TF),
|
||||
rbtree(TF),
|
||||
format("done ~d~n",[X]),
|
||||
fail.
|
||||
test_neg.
|
||||
|
||||
build_ntree(X,X,T0,TF) :- !,
|
||||
X1 is -X,
|
||||
insert(T0,X1,X1,TF).
|
||||
build_ntree(X1,X,T0,TF) :-
|
||||
NX1 is -X1,
|
||||
insert(T0,NX1,NX1,TI),
|
||||
X2 is X1+1,
|
||||
build_ntree(X2,X,TI,TF).
|
||||
|
||||
|
||||
|
||||
Reference in New Issue
Block a user