Question

使用Prolog语言，我需要找出一个数字中子序列的出现次数。

我试图在一个大文本文件中计算一个单词的出现次数，但它也没有用。虽然我有代码。

word_freq(W, Freq) :-
    word_count(W, 0, Total, 0, Match),
    Total > 0 -> Freq is Match / Total.

word_count(W, TotSoFar, Tot, MatchSoFar, Match) :-
    (  read_word(SoFar,W),
    N \= end_of_file
    -> T1 is TotSoFar + 1,
    (  N == W
    -> M1 is MatchSoFar+1
    ;  M1 is MatchSoFar
    ),
    word_count(W, T1, Tot, M1, Match)
    ; TotSoFar = Tot,
    MatchSoFar = Match
    ).

read_word(SoFar, W) :-
    get_code(C),
    (   C == -1
    ->  ( SoFar == [] -> W = end_of_file ; reverse(SoFar, W) )
    ;   code_type(C, alnum)
    ->  read_word([C|SoFar], W)
    ;   reverse(SoFar, W)
    ).

我认为两者或类似的事件/频率计数应该相同。我不知道从哪里开始或如何继续，感谢任何帮助。

Answer 1

让我知道您对此解决方案的看法。我假设子序列也必须是一个数字，因为我们正在寻找它的出现次数。

这个想法如下：

给定一个数字和另一个数字（子序列），从数字中减去子序列，并查看最低有效数字是否为零（最低有效数字的数量由子序列的大小确定）。如果它们是零，那么我们有后续，否则我们没有。继续使用NumberNew = Number div 10获得的其余数字执行此操作，直到达到Number小于Subsequence的情况。如果您在理解代码时遇到任何问题，我将编辑帖子并使用评论进行更新。

subsequence_size(Subsequence,1) :- Subsequence < 10,!.
subsequence_size(Subsequence,Size) :- SubNew is Subsequence div 10,subsequence_size(SubNew,N),Size is N+1. 


is_subsequence(_,0).
is_subsequence(Number,SubSize) :-  Rem is Number mod 10,
                                   Rem=0,
                                   NumberNew is Number div 10,
                                   SubSizeNew is SubSize - 1,
                                   is_subsequence(NumberNew,SubSizeNew).

occurence_of_subsequence_in_number(Subsequence,Number,Occurences) :- subsequence_size(Subsequence,SubSize),
                                                                     count(Subsequence,SubSize,Number,0,Occurences).

count(0,_,0,Occurences,1) :- Occurences=0,!.
count(0,_,0,Occurences,Occurences) :- not(Occurences=0),!.
count(Subsequence,_,Number,Occurences,Occurences) :- Subsequence > Number,!.
count(Subsequence,SubSize,Number,Occurences,FinalOccurences) :- NumberToTest is Number-Subsequence,
                                                                (is_subsequence(NumberToTest,SubSize)),
                                                                OccurencesNew is Occurences+1,
                                                                NumberNew is Number div 10,
                                                                count(Subsequence,SubSize,NumberNew,OccurencesNew,FinalOccurences),!.

count(Subsequence,SubSize,Number,Occurences,FinalOccurences) :- NumberToTest is Number-Subsequence,
                                                                not(is_subsequence(NumberToTest,SubSize)),
                                                                NumberNew is Number div 10,
                                                                count(Subsequence,SubSize,NumberNew,Occurences,FinalOccurences),!.

PROLOG-将子序列出现在一个数字中

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