commit e1d5368d5edac77d26bbbc1ffd9cfc9c193a1c69
parent 996ef798572c535a87ecb57321b51961da2620c1
Author: Natasha Kerensikova <natgh@instinctive.eu>
Date: Sat, 14 Dec 2024 23:12:27 +0000
Day 14 reference and solutions
Diffstat:
2 files changed, 125 insertions(+), 0 deletions(-)
diff --git a/2024/day14.nim b/2024/day14.nim
@@ -0,0 +1,113 @@
+# Copyright (c) 2024, Natacha Porté
+#
+# Permission to use, copy, modify, and distribute this software for any
+# purpose with or without fee is hereby granted, provided that the above
+# copyright notice and this permission notice appear in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+from std/math import euclMod, lcm
+from std/sequtils import allIt, foldl, map, mapIt, newSeqWith, toSeq
+from std/strutils import join, parseInt, split
+
+# Read input file
+
+type
+ Point = tuple
+ x, y: int
+ Robot = tuple
+ p, v: Point
+
+func process_line(s: string): Robot =
+ let h = s.split(" ")
+ assert len(h) == 2
+ assert h[0][0 .. 1] == "p="
+ assert h[1][0 .. 1] == "v="
+ let
+ p1 = h[0][2 .. ^1].split(",")
+ p2 = h[1][2 .. ^1].split(",")
+ assert len(p1) == 2
+ assert len(p2) == 2
+ result = (p: (x: parseInt(p1[0]), y: parseInt(p1[1])), v: (x: parseInt(p2[0]), y: parseInt(p2[1])))
+
+let
+ data = stdin.lines().toSeq().map(process_line)
+ xlen = max(data.mapIt(it.p.x)) + 1
+ ylen = max(data.mapIt(it.p.y)) + 1
+
+# Puzzle 1
+
+func forward(r: Robot, t, xmod, ymod: int): Robot =
+ (p: (x: euclMod(r.p.x + t * r.v.x, xmod), y: euclMod(r.p.y + t * r.v.y, ymod)), v: r.v)
+
+func safety_factor(s: seq[Robot], xmod, ymod: int): int =
+ assert xmod mod 2 == 1
+ assert ymod mod 2 == 1
+ let
+ hx = (xmod - 1) div 2
+ hy = (ymod - 1) div 2
+ var q = @[0, 0, 0, 0]
+ for r in s:
+ if r.p.y < hy:
+ if r.p.x < hx:
+ q[0] += 1
+ elif r.p.x > hx:
+ q[1] += 1
+ elif r.p.y > hy:
+ if r.p.x < hx:
+ q[2] += 1
+ elif r.p.x > hx:
+ q[3] += 1
+ result = q.foldl(a * b)
+
+echo "Puzzle 1: ", data.mapIt(forward(it, 100, xlen, ylen)).safety_factor(xlen, ylen)
+
+# Puzzle 2
+
+func display_char(i: int): char =
+ case i
+ of 0:
+ result = '.'
+ of 1 .. 9:
+ result = ($i)[0]
+ else:
+ result = '*'
+
+proc display(s: seq[Robot], xmod, ymod: int): void =
+ var map = newSeqWith(ymod, newSeqWith(xmod, 0))
+ for r in s:
+ map[r.p.y][r.p.x] += 1
+ for line in map:
+ echo line.map(display_char).join()
+
+proc is_tree(s: seq[Robot], xmod, ymod: int): bool =
+ assert xmod mod 2 == 1
+ assert ymod mod 2 == 1
+ # use a horizontal segment as a proxy for tree-likeness
+ let line_size = 11
+ var map = newSeqWith(ymod, newSeqWith(xmod, 0))
+ for r in s:
+ map[r.p.y][r.p.x] += 1
+ for y in 0 ..< ymod:
+ for x in 0 .. xmod - line_size - 1:
+ if map[y][x ..< x + line_size].allIt(it > 0):
+ for line in map:
+ echo line.map(display_char).join()
+ return true
+
+proc find_tree(s0: seq[Robot], xmod, ymod: int): int =
+ var s = s0
+ result = 0
+ while not is_tree(s, xmod, ymod):
+ s = s.mapIt(forward(it, 1, xmod, ymod))
+ result += 1
+ if result > lcm(xmod, ymod):
+ return -1
+
+echo "Puzzle 2: ", find_tree(data, xlen, ylen)
diff --git a/2024/ref/day14.txt b/2024/ref/day14.txt
@@ -0,0 +1,12 @@
+p=0,4 v=3,-3
+p=6,3 v=-1,-3
+p=10,3 v=-1,2
+p=2,0 v=2,-1
+p=0,0 v=1,3
+p=3,0 v=-2,-2
+p=7,6 v=-1,-3
+p=3,0 v=-1,-2
+p=9,3 v=2,3
+p=7,3 v=-1,2
+p=2,4 v=2,-3
+p=9,5 v=-3,-3
