feat: 2023 day 24

Author: Programator2

2023/24.txt

@@ -0,0 +1 @@
+2

2023/24_expa.txt

@@ -0,0 +1 @@
+47

2023/24_expb.txt

@@ -0,0 +1,5 @@
+19, 13, 30 @ -2,  1, -2
+18, 19, 22 @ -1, -1, -2
+20, 25, 34 @ -2, -2, -4
+12, 31, 28 @ -1, -2, -1
+20, 19, 15 @  1, -5, -3

2023/24_test.txt

@@ -0,0 +1,45 @@
+from aoc import *
+from itertools import combinations
+from sympy import *
+from sympy.geometry import *
+
+
+def main(input_file: str):
+    inp = lines(input_file)
+    points = []
+    for l in inp:
+        left, right = l.split(' @ ')
+        left = tuple(int(x) for x in left.split(', '))
+        right = tuple(int(x) for x in right.split(', '))
+        points.append((left, right))
+
+    x_min = 200000000000000
+    x_max = 400000000000000
+
+    # For test input
+    # x_min = 7
+    # x_max = 27
+
+    suma = 0
+    for ((x, y, z), (a, b, c)), ((i, j, k), (d, e, f)) in combinations(points, 2):
+        q = Point(x, y)
+        w = Point(x + a, y + b)
+        l1 = Line(q, w)
+        l1 = Ray(q, w)
+        r = Point(i, j)
+        t = Point(i + d, j + e)
+        l2 = Line(r, t)
+        l2 = Ray(r, t)
+        inter = intersection(l1, l2)
+        if inter:
+            if x_min <= inter[0][0] <= x_max and x_min <= inter[0][1] <= x_max:
+                suma += 1
+    return suma
+
+DAY = 24
+FILE_TEST = f"{DAY}_test.txt"
+FILE_EXP = f"{DAY}_expa.txt"
+FILE = f"{DAY}.txt"
+# test_and_submit(main, FILE_TEST, FILE_EXP, FILE, DAY)
+# print(main(FILE_TEST))
+print(main(FILE))

2023/24a.py

@@ -1,81 +1,48 @@
 from aoc import *
-from statistics import median, mode
-from more_itertools import windowed, take, peekable, chunked, first_true, split_when, first_true
-from heapq import *
-# from functools import reduce, cache, cmp_to_key
-from functools import cache
-from math import ceil
-import re
-from blessed import BlessedList
-from copy import deepcopy
-import operator
-from string import ascii_letters, ascii_lowercase, ascii_uppercase, digits, hexdigits, whitespace
-from pprint import pprint as pp
-import bisect
-import math
-from itertools import pairwise, combinations
-import sys
-from collections import defaultdict, OrderedDict, deque, Counter
-# from ordered_set import OrderedSet
-from sympy import *
-from sympy.geometry import *
+from sympy import symbols
+from sympy.solvers.polysys import solve_poly_system
 
 
+# Geometrical representation: H is a set of lines (more precisely rays, but this
+# doesn't matter in this task) that represent the trajectories of hailstones. We
+# have to find line l (trajectory of our stone) that intersects all lines in H.
+#
+# This can be represented analytically as a system of equations (they aren't
+# linear as there is a multiplication of two unknowns).
+#
+# As line is defined by two points, if we find a unique line that intersects
+# three lines from H, it should also intersect all other lines (considering the
+# input is correct).
+#
+# Many people on r/adventofcode used Z3. I wanted to use a Python solution and
+# since I used sympy for part one, this post was a good inspiration for me:
+# https://www.reddit.com/r/adventofcode/comments/18pnycy/comment/kepmry2/?utm_source=share&utm_medium=web2x&context=3
 def main(input_file: str):
     inp = lines(input_file)
     points = []
-    for l in inp:
+    system = []
+    x, y, z, vx, vy, vz = symbols('x y z vx vy vz')
+    ts = []
+    # Three lines (points) is enough. It will define the throw line for all
+    # other hailstones.
+    for i, l in enumerate(inp[:3]):
         left, right = l.split(' @ ')
-        left = tuple(int(x) for x in left.split(', '))
-        right = tuple(int(x) for x in right.split(', '))
+        left = tuple(int(j) for j in left.split(', '))
+        right = tuple(int(j) for j in right.split(', '))
         points.append((left, right))
+        t = symbols(f't{i}')
+        ts.append(t)
+        system.append(x + vx * t - left[0] - right[0] * t)
+        system.append(y + vy * t - left[1] - right[1] * t)
+        system.append(z + vz * t - left[2] - right[2] * t)
 
-    x_min = 200000000000000
-    x_max = 400000000000000
-    # x_min = 7
-    # x_max = 27
-    suma = 0
-    time = []
-    for i in range(1, 4):
-        new_points = []
-        for (x, y, z), (a, b, c) in points:
-            new_points.append((x+a*i, y+b*i, z+c*i))
-        time.append(new_points)
-    for i1, p1 in enumerate(time[0]):
-        for i2, p2 in enumerate(time[1]):
-            if i2 == i1:
-                continue
-            for i3, p3 in enumerate(time[2]):
-                if i3 in [i1, i2]:
-                    continue
-                q = Point(p1)
-                w = Point(p2)
-                line = Line(q, w)
-                if line.intersection(Point(p3)):
-                    print(p1, p2, p3)
+    return sum(solve_poly_system(system, x, y, z, vx, vy, vz, *ts)[0][:3])
 
-    # for ((x, y, z), (a, b, c)), ((i, j, k), (d, e, f)) in combinations(points, 2):
-    #     q = Point(x, y)
-    #     w = Point(x + a, y + b)
-    #     # w = Point(a, b)
-    #     l1 = Line(q, w)
-    #     l1 = Ray(q, w)
-    #     r = Point(i, j)
-    #     t = Point(i + d, j + e)
-    #     # t = Point(d, e)
-    #     l2 = Line(r, t)
-    #     l2 = Ray(r, t)
-    #     inter = intersection(l1, l2)
-    #     if inter:
-    #         if x_min <= inter[0][0] <= x_max and x_min <= inter[0][1] <= x_max:
-    #             suma += 1
-    #             # print(f'{((x, y, z), (a, b, c)), ((i, j, k), (d, e, f))}: will cross at {inter}')
-    return
 
 DAY = 24
 FILE_TEST = f"{DAY}_test.txt"
 FILE_EXP = f"{DAY}_expa.txt"
 FILE = f"{DAY}.txt"
 # test_and_submit(main, FILE_TEST, FILE_EXP, FILE, DAY)
-# print(main(FILE_TEST))
+print(main(FILE_TEST))
 print(main(FILE))