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Day 8 - Advent of Code 2023

lib/advent_of_code/2023/day-08.livemd

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Tyler Johnson
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Day 8 - Advent of Code 2023

Mix.install([
  {:kino, "~> 0.11.3"},
  {:benchee, "~> 1.2"},
  {:math, "~> 0.7.0"}
])

Links

Input

input = Kino.Input.textarea("Please paste your input file:")
input = input |> Kino.Input.read()
# input = AdventOfCode.Input.get!(8, 2023)
"LLRLLRLRLRRRLLRRRLRRLRLRLRLRLRLRRLRRRLRLLRRLRRLRRRLLRLLRRLLRRRLLLRLRRRLLLLRRRLLRRRLRRLRLLRLRLRRRLRRRLRRLRRLRRLRLLRRRLRRLRRRLLRRRLRLRRLLRRLLRLRLRRLRRLLRLLRRLRLLRRRLLRRRLRRLLRRLRRRLRLRRRLRRLLLRLLRLLRRRLRLRLRLRRLRRRLLLRRRLRRRLRRRLRRLRLRLRLRRRLRRLLRLRRRLRLRLRRLLLRRRR\n\nTFN = (SMC, LQT)\nJKL = (XDN, KPK)\nJMF = (HGP, QKF)\nRJR = (VMR, RRM)\nFJS = (RMD, HSP)\nQKS = (KDN, KDN)\nVTN = (PQR, LVV)\nPNS = (SDG, XJF)\nRQC = (TDX, DSD)\nHSH = (QTK, VDS)\nSSM = (NFM, PRT)\nFDX = (JJJ, SCZ)\nMHS = (PBJ, THP)\nDPV = (KXL, STJ)\nHVP = (DPV, RGP)\nTPN = (TJC, KMC)\nTFD = (QVD, DRT)\nHQH = (TMT, SXJ)\nHGP = (TNG, GMK)\nFCC = (HGB, MLQ)\nMDJ = (CCH, HMG)\nQKF = (GMK, TNG)\nDBP = (FNP, TRB)\nQNQ = (SKD, HRG)\nVGC = (LFV, TVS)\nNQD = (PTD, TCM)\nGSQ = (PPP, KHS)\nLKC = (QKG, TTL)\nFDD = (TRX, NKV)\nQMG = (QSR, SDR)\nSXD = (DNN, KJC)\nNXD = (RLB, RLB)\nSBP = (PRG, CXT)\nXDM = (RKH, VRF)\nGHD = (JLX, VXS)\nXJV = (VXS, JLX)\nGXX = (TDJ, NXP)\nDMQ = (SLH, RTD)\nSMC = (RFR, DPS)\nBBC = (HPF, CJL)\nGVZ = (CQJ, HRT)\nMMT = (VPH, MGD)\nLCQ = (HSH, TPX)\nNXC = (NXP, TDJ)\nNLL = (VJM, QTP)\nNQZ = (CRR, KCL)\nKLT = (SFS, PSM)\nSDR = (FBB, KGM)\nGCS = (HNQ, BDH)\nHLJ = (JXV, SPG)\nSRP = (XXC, RKP)\nQJH = (XDC, DBP)\nXJF = (NHT, SLL)\nQCD = (RQM, LCQ)\nQSS = (KHD, QMG)\nXNJ = (FJS, GLF)\nPFH = (NSP, HSG)\nVVD = (JLQ, VKF)\nPNT = (PXQ, CMM)\nPJG = (DBP, XDC)\nTTL = (LFS, NHL)\nGJM = (HVL, GMF)\nBGM = (QBK, SKV)\nDXD = (GNN, HQH)\nJPP = (QHM, DXD)\nLPH = (JKS, HBQ)\nCDG = (LXQ, KTC)\nPLF = (HGG, LRS)\nJJP = (SRQ, NQD)\nPBH = (CMM, PXQ)\nHGD = (XGK, XCL)\nNNM = (GTK, XCB)\nTFG = (JHM, JMK)\nVDQ = (PSM, SFS)\nNDP = (CGF, LBM)\nCGF = (KVF, TVM)\nKDN = (KCL, CRR)\nRQM = (HSH, TPX)\nJKB = (JPP, VGH)\nXDC = (FNP, TRB)\nVDF = (BKD, NQQ)\nTKN = (VGM, BDK)\nNSN = (GJV, SPB)\nDSD = (QVK, MVX)\nVFX = (PKM, VTN)\nFRC = (JBH, BCK)\nXKX = (PNS, CVL)\nVRF = (QHR, FDX)\nJCV = (BGP, BGP)\nJRC = (JKV, NBL)\nHNQ = (QNQ, HFB)\nBMV = (DBV, CFH)\nFTC = (PKM, VTN)\nKHS = (TFD, VPM)\nJQX = (VBL, PPX)\nHGM = (NFM, PRT)\nBGD = (LCQ, RQM)\nPSM = (KJB, SJH)\nVXL = (TDB, HGD)\nLKT = (LDB, MMT)\nRJV = (CJL, HPF)\nJBF = (FJC, QHH)\nRBV = (QKS, CTD)\nGBL = (DCX, JRF)\nXVX = (XGT, DCJ)\nGSD = (JMG, CVR)\nRGP = (STJ, KXL)\nHRV = (LPG, DMQ)\nVPH = (PQF, KLF)\nSTP = (NMG, BXH)\nTTH = (HMV, NCR)\nMLQ = (SFP, GCS)\nRCR = (LBM, CGF)\nCCB = (HQB, VSQ)\nQGL = (RRS, RRS)\nHVL = (LDR, CXN)\nQKG = (NHL, LFS)\nXGN = (HGG, LRS)\nJCG = (KBS, QLP)\nPVX = (XHG, XPC)\nTPD = (TDH, QLT)\nXQG = (NXD, KSK)\nKHL = (GQX, TSK)\nGVF = (VBJ, DJL)\nSGB = (XXC, RKP)\nRKD = (BNP, PTZ)\nQNS = (JKS, HBQ)\nJXV = (BQX, PKN)\nJVJ = (SRQ, NQD)\nVLG = (BJL, MTP)\nVLJ = (KBP, VGC)\nHQL = (PLF, XGN)\nDTR = (SKV, QBK)\nGJV = (HLP, DQR)\nDTX = (GBQ, XDM)\nTDH = (KBL, PRK)\nKLF = (RPC, BMG)\nLBQ = (NRF, MGJ)\nXHG = (FBL, JMF)\nCBC = (TNT, TJS)\nSVP = (LTD, JQX)\nKCC = (NMX, NBF)\nNFS = (HVL, GMF)\nGMH = (RND, CSJ)\nFVF = (QVH, XLR)\nNHK = (MQT, HFR)\nNBN = (VMR, RRM)\nCSD = (CSK, JPS)\nVQL = (THK, SXT)\nHFB = (SKD, HRG)\nKHD = (QSR, SDR)\nNLV = (SDB, DDZ)\nCNP = (JHX, PDP)\nPRK = (KPS, DDS)\nCQB = (BBP, GCQ)\nPCJ = (JRF, DCX)\nHSG = (JCV, NTF)\nSXJ = (CML, RKD)\nSFP = (HNQ, BDH)\nDDZ = (GXX, NXC)\nHLR = (NKV, TRX)\nBJL = (XPH, MSC)\nJFS = (KJC, DNN)\nNPH = (TBX, QCG)\nKBR = (PJX, GVF)\nJQH = (VNT, KBT)\nMBX = (PTB, BMR)\nNXR = (JBT, KMD)\nNCR = (PMB, MJR)\nTHP = (BRT, FDV)\nRNG = (KJN, KTH)\nRPC = (PRR, RBC)\nXMR = (LSD, BMM)\nHMG = (SSM, HGM)\nPCH = (QJH, PJG)\nMMG = (NBF, NMX)\nQBJ = (HNS, JNR)\nKBL = (DDS, KPS)\nVBJ = (XJV, GHD)\nGHT = (CVL, PNS)\nVGH = (QHM, DXD)\nGTK = (NCX, CCB)\nBMR = (GMD, FHH)\nFDV = (MBK, VJQ)\nBKD = (CBQ, RVM)\nQTP = (TXR, FVX)\nVBL = (HMR, QFM)\nQTK = (TPB, SHF)\nRTD = (JRC, RNF)\nQFR = (MDP, HTC)\nMSF = (CSK, JPS)\nPKM = (PQR, LVV)\nVHK = (KHD, QMG)\nVGL = (BCK, JBH)\nVNT = (VKH, NLP)\nKXN = (VCN, VPS)\nHSP = (TMC, CMT)\nLSD = (GHT, XKX)\nLGN = (GNL, JDP)\nQGC = (QLT, TDH)\nNKV = (XPS, LKJ)\nDJK = (KTH, KJN)\nBCK = (NCF, MCQ)\nFDS = (PSD, RBQ)\nSCZ = (TDV, FKM)\nPGQ = (DSV, NJR)\nPTD = (VVD, BTH)\nSLK = (SMB, GSQ)\nMJR = (DMB, MBC)\nBGC = (HRQ, MVB)\nXLN = (QSS, VHK)\nKFG = (MRB, JQL)\nNQB = (TRR, SMV)\nFMV = (PBJ, THP)\nQGJ = (QQB, KNC)\nPQR = (LTS, VDF)\nTHK = (NCK, DKX)\nTDX = (QVK, MVX)\nQCN = (DHN, STP)\nKJN = (QGX, TQC)\nCBS = (QSS, VHK)\nDNN = (XQG, HGN)\nBQX = (SXD, JFS)\nCMT = (JGJ, NRC)\nFJC = (FSB, LRK)\nTPB = " <> ...

Solution

defmodule Day08 do
  defdelegate parse(input), to: __MODULE__.Input

  def part1(input) do
    {turns, nodes} = parse(input)

    step_count("AAA", turns, nodes, &amp;(&amp;1 == "ZZZ"))
  end

  def part2(input) do
    {turns, nodes} = parse(input)

    nodes
    |> Map.keys()
    |> Enum.filter(&amp;String.ends_with?(&amp;1, "A"))
    |> Enum.map(fn start_node ->
      step_count(start_node, turns, nodes, &amp;String.ends_with?(&amp;1, "Z"))
    end)
    |> Enum.reduce(1, &amp;Math.lcm/2)
  end

  defp step_count(start_node, turns, nodes, end_fun) do
    step_count(start_node, 0, turns, turns, nodes, end_fun)
  end

  defp step_count(current, count, [], turns, nodes, end_fun) do
    step_count(current, count, turns, turns, nodes, end_fun)
  end

  defp step_count(current, count, [next_turn | tail], turns, nodes, end_fun) do
    if end_fun.(current) do
      count
    else
      next_node(next_turn, nodes, current)
      |> step_count(count + 1, tail, turns, nodes, end_fun)
    end
  end

  defp next_node(?L, nodes, current) do
    nodes[current] |> elem(0)
  end

  defp next_node(?R, nodes, current) do
    nodes[current] |> elem(1)
  end

  defmodule Input do
    def parse(input) when is_binary(input) do
      input
      |> String.split("\n", trim: true)
      |> parse()
    end

    def parse(input) do
      [turns | nodes] = input

      {
        String.to_charlist(turns),
        Enum.map(nodes, &amp;parse_line/1) |> Enum.into(%{})
      }
    end

    def parse_line(line) do
      [key, left, right] = String.split(line, [" = (", ")", ", "], trim: true)

      {key, {left, right}}
    end
  end
end
{:module, Day08, <<70, 79, 82, 49, 0, 0, 14, ...>>,
 {:module, Day08.Input, <<70, 79, 82, ...>>, {:parse_line, 1}}}

Starting at AAA, follow the left/right instructions. How many steps are required to reach ZZZ?

Your puzzle answer was 20777.

Day08.part1(input)
20777

Simultaneously start on every node that ends with A. How many steps does it take before you’re only on nodes that end with Z?

Your puzzle answer was 13289612809129.

Day08.part2(input)
13289612809129

Both parts of this puzzle are complete! They provide two gold stars: **

At this point, you should return to your Advent calendar and try another puzzle.

If you still want to see it, you can get your puzzle input.

Tests

ExUnit.start(auto_run: false)

defmodule Day08Test do
  use ExUnit.Case, async: false

  setup_all do
    [
      input1a:
        "RL\n\nAAA = (BBB, CCC)\nBBB = (DDD, EEE)\nCCC = (ZZZ, GGG)\nDDD = (DDD, DDD)\nEEE = (EEE, EEE)\nGGG = (GGG, GGG)\nZZZ = (ZZZ, ZZZ)",
      input1b: "LLR\n\nAAA = (BBB, BBB)\nBBB = (AAA, ZZZ)\nZZZ = (ZZZ, ZZZ)",
      input2:
        "LR\n\n11A = (11B, XXX)\n11B = (XXX, 11Z)\n11Z = (11B, XXX)\n22A = (22B, XXX)\n22B = (22C, 22C)\n22C = (22Z, 22Z)\n22Z = (22B, 22B)\nXXX = (XXX, XXX)"
    ]
  end

  describe "part1/1" do
    test "returns expected value", %{input1a: input1a, input1b: input1b} do
      assert Day08.part1(input1a) == 2
      assert Day08.part1(input1b) == 6
    end
  end

  describe "part2/1" do
    test "returns expected value", %{input2: input2} do
      assert Day08.part2(input2) == 6
    end
  end
end

ExUnit.run()
..
Finished in 0.00 seconds (0.00s async, 0.00s sync)
2 tests, 0 failures

Randomized with seed 254250
%{total: 2, failures: 0, excluded: 0, skipped: 0}

Benchmarking

# https://github.com/bencheeorg/benchee
Benchee.run(
  %{
    "Part 1" => fn -> Day08.part1(input) end,
    "Part 2" => fn -> Day08.part2(input) end
  },
  memory_time: 2,
  reduction_time: 2
)

nil
Warning: the benchmark Part 1 is using an evaluated function.
  Evaluated functions perform slower than compiled functions.
  You can move the Benchee caller to a function in a module and invoke `Mod.fun()` instead.
  Alternatively, you can move the benchmark into a benchmark.exs file and run mix run benchmark.exs

Warning: the benchmark Part 2 is using an evaluated function.
  Evaluated functions perform slower than compiled functions.
  You can move the Benchee caller to a function in a module and invoke `Mod.fun()` instead.
  Alternatively, you can move the benchmark into a benchmark.exs file and run mix run benchmark.exs

Operating System: macOS
CPU Information: Apple M1 Pro
Number of Available Cores: 10
Available memory: 32 GB
Elixir 1.15.6
Erlang 26.1

Benchmark suite executing with the following configuration:
warmup: 2 s
time: 5 s
memory time: 2 s
reduction time: 2 s
parallel: 1
inputs: none specified
Estimated total run time: 22 s

Benchmarking Part 1 ...
Benchmarking Part 2 ...

Name             ips        average  deviation         median         99th %
Part 1        407.25        2.46 ms     ±1.30%        2.45 ms        2.58 ms
Part 2        117.59        8.50 ms     ±0.99%        8.48 ms        8.82 ms

Comparison: 
Part 1        407.25
Part 2        117.59 - 3.46x slower +6.05 ms

Memory usage statistics:

Name      Memory usage
Part 1       160.71 KB
Part 2       173.02 KB - 1.08x memory usage +12.31 KB

**All measurements for memory usage were the same**

Reduction count statistics:

Name           average  deviation         median         99th %
Part 1        180.05 K     ±0.01%       180.05 K       180.08 K
Part 2        900.35 K     ±0.00%       900.35 K       900.39 K

Comparison: 
Part 1        180.05 K
Part 2        900.35 K - 5.00x reduction count +720.30 K
nil
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