Teaching and learning resources • Re: Advent of Code 2023

Code:

julia> include("day08.jl")Advent of Code 2023 Day 8 Haunted WastelandPart 1 The total number of steps is 22411Part 2 The number of ghost steps is 11188774513823Total execution time 5.906414466 seconds.julia> main()Advent of Code 2023 Day 8 Haunted WastelandPart 1 The total number of steps is 22411Part 2 The number of ghost steps is 11188774513823Total execution time 3.521387046 seconds.julia> main()Advent of Code 2023 Day 8 Haunted WastelandPart 1 The total number of steps is 22411Part 2 The number of ghost steps is 11188774513823Total execution time 3.678939884 seconds.

Code:

#=  Advent of Code 2023 Day 8 Haunted Wasteland    Written 2023 by Eric Olson =#struct DoExit <: Exceptionendfunction gobble(s::String,m::String)::Tuple{String,Bool}    if length(s)<length(m)        return s,false    end    if s[1:length(m)]==m        return s[length(m)+1:end],true    end    return s,falseendfunction wskip(s::String)::String    for i=1:length(s)        if !isspace(s[i])            return s[i:end]        end    end    return ""endfunction vskip(data,i::Int)::Int    while i<=length(data)&&length(data[i])==0        i+=1    end    return iend function getalpha(s::String)::Tuple{String,String}    for i=1:length(s)        if !isletter(s[i])            return s[i:end],s[1:i-1]        end    end    return "",sendfunction getint(s::String)::Tuple{String,Int64}    n=Int64(0)    for i=1:length(s)        if s[i]>='0'&&s[i]<='9'            n=n*10+Int64(s[i]-'0')        else            return s[i:end],n        end    end    return "",nendfunction getelement(s::String)::Vector{String}    b=s    s,a=getalpha(s)    if length(a)==0        println("$b\nUnable to parse node name!")        throw(DoExit())    end    s,f=gobble(s," = (")    if !f        println("$b\nMissing ' = (' in node table!")        throw(DoExit())    end    s,l=getalpha(s)    if length(l)==0        println("$b\nUnable to parse left node name!")        throw(DoExit())    end    s,f=gobble(s,", ")    if !f        println("$b\nMissing ', ' in node table!")        throw(DoExit())    end    s,r=getalpha(s)    if length(l)==0        println("$b\nUnable to parse right node name!")        throw(DoExit())    end    s,f=gobble(s,")")    if !f        println("$b\nMissing ')' in node table!")        throw(DoExit())    end    if length(s)>0        println("$b\nCharacters after node description!")        throw(DoExit())    end    return [a,l,r]endmutable struct Node    s::Vector{String}    l::Union{Node,Nothing}    r::Union{Node,Nothing}endfunction mknavi(s::String)    i::Int=0    navi=let i=i        function navi(j::Int=1)::Char            if j==0                i=0                return s[1]            end            i+=1            if i>length(s)                i=1            end            return s[i]        end    end    return naviendfunction part1(m::Dict{String,Node},navi::Function)::Int    navi(0)    q=m["AAA"]    c=0    while q.s[1]!="ZZZ"        d=navi()        if d=='L'            q=q.l        elseif d=='R'            q=q.r        else            println("Unknown direction $d in navigation!")            throw(DoExit())        end        c+=1    end    return cendfunction part2(m::Dict{String,Node},navi::Function)::Int64    function qstep(q::Node,d::Char)::Node        if d=='L'            return q.l        elseif d=='R'            return q.r        else            println("Unknown direction $d in navigation!")            throw(DoExit())        end    end    function sloop(q::Node)::Tuple{Int,Node}        c=0        while q.s[1][end]!='Z'            d=navi()            q=qstep(q,d)            c+=1        end        return c,q    end    v=Int64[]    for (_,q) in m        if q.s[1][end]=='A'            navi(0)            p=q            c1,p=sloop(p)            c,p=sloop(qstep(p,navi()))            c2=c+1            c,p=sloop(qstep(p,navi()))            c3=c+1            if c1!=c2||c2!=c3                println("Assumption about uniform cycles not met!")                dothrow(DoExit())            end            push!(v,c1)        end    end    return lcm(v)endfunction doinit()    data=[]    open("day08.txt","r") do fp        data=readlines(fp)    end    m=Dict{String,Node}()    nodes=Vector{Node}(undef,length(data)-2)    for i=3:length(data)        v=getelement(data[i])        m[v[1]]=Node(v,nothing,nothing)    end    for (k,p) in m        p.l=m[p.s[2]]        p.r=m[p.s[3]]    end    navi=mknavi(data[1])    p1=part1(m,navi)    p2=part2(m,navi)    println("Part 1 The total number of steps is ",p1)    println("Part 2 The number of ghost steps is ",p2)endfunction main()    t=@elapsed try        println("Advent of Code 2023 Day 8 Haunted Wasteland\n")        doinit()        throw(DoExit())    catch r        if !isa(r,DoExit)            rethrow(r)        end    end    println("\nTotal execution time ",t," seconds.")end main()