p2.jl

using Dates
using DataStructures

file = open("input")
lines = readlines(file)
parseInt = x -> parse(Int, x)

function parse_line(line::String)
  regex = r"\[(?<year>\d+)-(?<month>\d+)-(?<day>\d+) (?<hour>\d+):(?<minute>\d+)\] (?<wakes>wakes up)*(?<sleep>falls asleep)*(?<shift>Guard #(?<gid>\d+) begins shift)*"
  m = match(regex, line)
  return (parseInt(m[:minute]), m[:wakes] != nothing, m[:sleep] != nothing, m[:gid])
end

function solve(lines::Vector{String})
  # sort dates
  lines = sort(lines)
  minutes_sleep_per_guard = DefaultDict{Int, Int}(0)
  minute_data = Dict(x => Int[] for x in 0:59)

  current_guard = nothing
  sleep_start = nothing
  for line in lines
    (minute, wakes, sleep, gid) = parse_line(line)

    if gid != nothing
      current_guard = parseInt(gid)
    end
    if sleep
      sleep_start = minute
    end
    if wakes
        for i in sleep_start:minute-1
          push!(minute_data[i], current_guard)
          minutes_sleep_per_guard[current_guard] += 1
        end
    end
  end

  function guard_max_minute(guard)
    max_minute = 0
    max_minute_slept = 0
    for (minute, guards) in minute_data
      count = filter(gid -> gid == guard, guards) |> length
      if count > max_minute_slept
        max_minute_slept = count
        max_minute = minute
      end
    end
    return (max_minute_slept, max_minute)
  end

  guards = keys(minutes_sleep_per_guard)
  mins_per_guard = Dict(guard => guard_max_minute(guard) for guard in guards)

  max_mins = 0
  guard_id = nothing
  for (guard, mins) in mins_per_guard
    if mins[1] > max_mins
      max_mins = mins[1]
      guard_id = guard
    end
  end

  return mins_per_guard[guard_id][2] * guard_id
end

println(solve(lines))