Teaching and learning resources • Re: Advent of Code 2023

Code:

julia> include("day21.jl") # Ryzen 4650Advent of Code 2023 Day 21 Step CounterPart 1 There are 3682 reachable garden plots.Part 2 On the infinite grid 609012263058042 are reachable.Total execution time 274.843657134 seconds.julia> main()Advent of Code 2023 Day 21 Step CounterPart 1 There are 3682 reachable garden plots.Part 2 On the infinite grid 609012263058042 are reachable.Total execution time 275.157613274 seconds.

Code:

#=  Advent of Code 2023 Day 21 Step Counter    Written 2024 by Eric Olson =#struct DoExit <: Exceptionendfunction pcount(A::Matrix{Char})::Int64    M,N=size(A)    s=0    for i=1:M        for j=1:N            if A[i,j]=='O'                s+=1            end        end    end        return sendfunction pclear(A::Matrix{Char})::Matrix{Char}    M,N=size(A)    B=Matrix{Char}(undef,M,N)    for j=1:N        for i=1:M            if A[i,j]=='O'                B[i,j]='.'            else                B[i,j]=A[i,j]            end        end    end    return Bendfunction walk(A::Matrix{Char})::Matrix{Char}    B=pclear(A)    M,N=size(B)    function gohere(i::Int,j::Int)        if j>N return end        if j<1 return end        if i>M return end        if i<1 return end        if B[i,j]=='.'            B[i,j]='O'        end    end    for i=1:M        for j=1:N            if A[i,j]=='O'                gohere(i,j+1)                gohere(i-1,j)                gohere(i,j-1)                gohere(i+1,j)            end        end    end    return Bendfunction StoO(c::Char)::Char    if c=='S'        return 'O'    end    return cendfunction part1(data::Vector{String})::Int64    M=length(data)    N=length(data[1])    A=[StoO(data[i][j]) for i=1:M,j=1:N]    for i=1:64        A=walk(A)    end    return pcount(A)endfunction reachable(A::Matrix{Char})::Vector{Int64}    saturated=false    i=1; c0=1; c1=0; c2=0    z=Int64[]    while !saturated        push!(z,c0)        A=walk(A); i+=1        c2=c1; c1=c0; c0=pcount(A)        if c0==c2            break        end    end    return zendfunction getpop(z::Vector{Int64},n::Int)::Int64    N=length(z)    if n<=N        return z[n]    else        m=(n+1-N)%2        return z[N-1+m]    endend#=  4  3  2    5  9  1    6  7  8  =#function toentry(i::Int,j::Int)::Int    if i==0        if j>0            return 1        elseif j<0            return 5        end        return 9    elseif i<0        if j>0            return 2        elseif j==0            return 3        end        return 4    end    if j<0        return 6    elseif j==0        return 7    end    return 8endfunction part2(data::Vector{String})::Int64    M=length(data)    N=length(data[1])    A=[StoO(data[i][j]) for i=1:M,j=1:N]    Z=Vector{Vector{Int64}}(undef,9)    Z[9]=reachable(A)    M2=(M+1)÷2; N2=(N+1)÷2    P=[[M2,N],[1,N],[1,N2],[1,1],[M2,1],[M,1],[M,N2],[M,N]]    for d=1:8        A=pclear(A)        A[P[d][1],P[d][2]]='O'        Z[d]=reachable(A)    end    s=26501365    sM=s÷M+1    sN=s÷N+1    t::Int64=0    for i=-sM:sM        for j=-sN:sN            c=s+1            if i>0                c+=-M2-M*(i-1)            elseif i<0                c+=-M2+M*(i+1)            end            if j>0                c+=-N2-N*(j-1)            elseif j<0                c+=-N2+N*(j+1)            end            if c>0                d=toentry(i,j)                t+=getpop(Z[d],c)            end        end    end    return tendfunction doinit()    data=String[]    open("day21.txt","r") do fp        data=readlines(fp)    end    p1=part1(data)    p2=part2(data)    println("Part 1 There are ",p1," reachable garden plots.")    println("Part 2 On the infinite grid ",p2," are reachable.")endfunction main()    t=@elapsed try        println("Advent of Code 2023 Day 21 Step Counter\n")        doinit()        throw(DoExit())    catch r        if !isa(r,DoExit)            rethrow(r)        end    end    println("\nTotal execution time ",t," seconds.")end main()

Code:

    for i=-sM:sM        for j=-sN:sN