advent-of-code-2024/solutions/day03/solution.nim

import std/[strutils, sequtils, math]
import aoc

proc parseInstruction(i: string): (int, int) =
  let s =  i.split(',')
  assert s.len == 2
  result = (parseInt(s[0]), parseInt(s[1]))

proc parseInput(input: string): seq[(int, int)] =
  var i: int
  while i < input.len:
    case input[i]
    of 'm':
      # ul(x,y)
      # not enough space so bail
      if i > (input.len - 6): return
      else:
        var instruction: string
        if input[i .. i+3] == "mul(":
          i += 4
          while true:
            let c = input[i]
            case c:
              of '0'..'9':
                instruction.add c; inc i
              of ')':
                result.add parseInstruction instruction
                break
              of ',':
                instruction.add c; inc i
              else: break
        inc i
    else: inc i

proc partOne*(input: string): int =
  let instructions = parseInput(input)
  instructions.mapIt(it[0] * it[1]).sum()

proc parseInput2(input: string): seq[(int, int)] =
  var i: int
  var working = true
  while i < input.len:
    case input[i]
    of 'd':
      # check for enough room for don't()
      if i > (input.len - 6): inc i
      else:
        if input[i .. i + 3] == "do()":
          working = true
          i += 3
        elif input[i .. i + 6] == "don't()":
          working = false
          i += 6
        inc i
    of 'm':
      # ul(x,y)
      # not enough space for instruction so bail
      if i > (input.len - 6): return
      else:
        var instruction: string
        if input[i .. i+3] == "mul(":
          i += 4
          while true:
            let c = input[i]
            case c:
              of '0'..'9':
                instruction.add c; inc i
              of ')':
                if working:
                  result.add parseInstruction instruction
                break
              of ',':
                instruction.add c; inc i
              else: break
        inc i
    else: inc i


proc partTwo*(input: string): int =
  let instructions = parseInput2(input)
  instructions.mapIt(it[0] * it[1]).sum()

solve:
  "example.txt":
    partOne: 161
  "example2.txt":
    partTwo: 48
  "input.txt":
    partOne: 164730528
    partTwo: 70478672