書き込み可能有限オートマトン

writableautomata.rb

# 
# 書き込み可能有限オートマトン
# WW^Rを受理する (w in {1,2,3})
# 
# OK 12311321
# OK 2222
# NG 123123

@tape=("$"+gets.chomp+"&").chars.to_a
@pos=1
@stat=0

@automata={}
@automata[[0,"1"]]=[1,1,"9"]
@automata[[0,"2"]]=[2,1,"9"]
@automata[[0,"3"]]=[3,1,"9"]
@automata[[1,"1"]]=[1,1,nil]
@automata[[1,"2"]]=[1,1,nil]
@automata[[1,"3"]]=[1,1,nil]
@automata[[1,"9"]]=[4,-1,nil]
@automata[[1,"&"]]=[4,-1,nil]
@automata[[2,"1"]]=[2,1,nil]
@automata[[2,"2"]]=[2,1,nil]
@automata[[2,"3"]]=[2,1,nil]
@automata[[2,"9"]]=[5,-1,nil]
@automata[[2,"&"]]=[5,-1,nil]
@automata[[3,"1"]]=[3,1,nil]
@automata[[3,"2"]]=[3,1,nil]
@automata[[3,"3"]]=[3,1,nil]
@automata[[3,"9"]]=[6,-1,nil]
@automata[[3,"&"]]=[6,-1,nil]
@automata[[4,"1"]]=[7,-1,"9"]
@automata[[5,"2"]]=[7,-1,"9"]
@automata[[6,"3"]]=[7,-1,"9"]
@automata[[7,"9"]]=[nil,0,nil] # exit
@automata[[7,"1"]]=[8,-1,nil]
@automata[[7,"2"]]=[8,-1,nil]
@automata[[7,"3"]]=[8,-1,nil]
@automata[[8,"1"]]=[8,-1,nil]
@automata[[8,"2"]]=[8,-1,nil]
@automata[[8,"3"]]=[8,-1,nil]
@automata[[8,"9"]]=[0,1,nil]

loop{
    char = @tape[@pos]
    nxt = @automata[[@stat,char]]
    
    p [@tape,@pos,@stat,char]
    
    if !nxt
        puts "NG";exit
    elsif nxt[0]==nil
        puts "OK";exit
    end
    @stat=nxt[0]
    @tape[@pos]=nxt[2] if nxt[2]
    @pos+=nxt[1]
}