Day 09 part 2

const ROPELEN = 10

type
  Vec2i = tuple
    x, y: int

var
  tails = newSeq[Vec2i](ROPELEN)
  posVisited: HashSet[Vec2i]

func dist(a, b: Vec2i): float =
  sqrt(((a.x - b.x) ^ 2  + (a.y - b.y) ^ 2).float)

func `-`(a, b: Vec2i): Vec2i =
  result.x = a.x - b.x
  result.y = a.y - b.y
  if result.x < -1: result.x = -1
  if result.x > 1: result.x = 1
  if result.y < -1: result.y = -1
  if result.y > 1: result.y = 1

func `+=`(a: var Vec2i, b: Vec2i) = 
  a.x = a.x + b.x
  a.y = a.y + b.y

func update(tail: var Vec2i, head: Vec2i) =
  if dist(tail, head) > 1.5: tail += head - tail

proc move(head: var Vec2i, i, j: int) =
  var 
    x = i
    y = j
  while x != 0 or y != 0:
    if x > 0:
      head.x.inc
      x.dec
    elif x < 0:
      head.x.dec
      x.inc
    elif y > 0:
      head.y.inc
      y.dec
    elif y < 0:
      head.y.dec
      y.inc
    for i in 0..<tails.len-1: tails[i+1].update(tails[i])
    posVisited.incl tails[tails.len-1]

posVisited.incl tails[0]  # Add the beggining position (0,0)

for line in "input.txt".lines:
  var steps: int
  if scanf(line, "L $i", steps): tails[0].move(-steps, 0)
  elif scanf(line, "R $i", steps): tails[0].move(steps, 0)
  elif scanf(line, "U $i", steps): tails[0].move(0, steps)
  elif scanf(line, "D $i", steps): tails[0].move(0, -steps)

Answer is: 2557

import strformat, strutils, sets, math import std/strscans import nimib const DAY = 9 PART = 2 DOCNAME = fmt"d{DAY:02}p{PART}" nbInit nb.title = DOCNAME nbText: fmt""" # Day {DAY:02} part {PART} """ nbCode: const ROPELEN = 10 type Vec2i = tuple x, y: int var tails = newSeq[Vec2i](ROPELEN) posVisited: HashSet[Vec2i] func dist(a, b: Vec2i): float = sqrt(((a.x - b.x) ^ 2 + (a.y - b.y) ^ 2).float) func `-`(a, b: Vec2i): Vec2i = result.x = a.x - b.x result.y = a.y - b.y if result.x < -1: result.x = -1 if result.x > 1: result.x = 1 if result.y < -1: result.y = -1 if result.y > 1: result.y = 1 func `+=`(a: var Vec2i, b: Vec2i) = a.x = a.x + b.x a.y = a.y + b.y func update(tail: var Vec2i, head: Vec2i) = if dist(tail, head) > 1.5: tail += head - tail proc move(head: var Vec2i, i, j: int) = var x = i y = j while x != 0 or y != 0: if x > 0: head.x.inc x.dec elif x < 0: head.x.dec x.inc elif y > 0: head.y.inc y.dec elif y < 0: head.y.dec y.inc for i in 0..<tails.len-1: tails[i+1].update(tails[i]) posVisited.incl tails[tails.len-1] posVisited.incl tails[0] # Add the beggining position (0,0) for line in "input.txt".lines: var steps: int if scanf(line, "L $i", steps): tails[0].move(-steps, 0) elif scanf(line, "R $i", steps): tails[0].move(steps, 0) elif scanf(line, "U $i", steps): tails[0].move(0, steps) elif scanf(line, "D $i", steps): tails[0].move(0, -steps) nbText: fmt""" Answer is: **{posVisited.len}** """ nb.filename = fmt"../../html/{DOCNAME}.html" nbSave