Day 15 part 1

const
  SCAN_Y = 2000000
type
  Dimension = tuple
    xmin, xmax, ymin, ymax: int
  Sensor = ref object
   x,y: int
   scanRange: Natural
  Beacon = ref object
    x, y: int

var
  answer: Natural
  mapDimensions: Dimension
  beaconsFound: seq[Beacon]

proc `notin`(coords: (int, int), beacons: seq[Beacon]): bool =
  result = true
  for b in beacons: 
    if b.x == coords[0] and b.y == coords[1]: return false

proc Covers(s: Sensor, x, y: int): bool =
  return abs(s.x - x) + abs(s.y - y) <= s.scanRange

proc newSensor(x, y, bx, by: int): Sensor =
  result = new Sensor
  result.x = x
  result.y = y
  result.scanRange = abs(x - bx) + abs(y - by)

proc loadObjects(): seq[Sensor] =
  for line in "input.txt".lines:
    var sx, sy, bx, by: int
    if not scanf(line, "Sensor at x=$i, y=$i: closest beacon is at x=$i, y=$i", sx, sy, bx, by): continue
    mapDimensions.xmin = min(mapDimensions.xmin, min(sx, bx))
    mapDimensions.ymin = min(mapDimensions.ymin, min(sy, by))
    mapDimensions.xmax = max(mapDimensions.xmax, max(sx, bx))
    mapDimensions.ymax = max(mapDimensions.ymax, max(sy, by))
    beaconsFound.add Beacon(x: bx, y: by)
    result.add newSensor(sx, sy, bx, by)

var sensors = loadObjects()

for x in mapDimensions.xmin..mapDimensions.xmax:
  for s in sensors:
    if s.Covers(x, SCAN_Y) and (x, SCAN_Y) notin beaconsFound:
      answer.inc
      break

Answer is: 5040643