From 5cffcf875c8189008dc8ee1a2bc07b0e8d4ff21b Mon Sep 17 00:00:00 2001
From: Gabriel Augendre <gabriel@augendre.info>
Date: Sun, 8 Nov 2020 15:44:37 +0100
Subject: [PATCH] Add day10

---
 2019/day10-asteroids.py | 73 +++++++++++++++++++++++++++++++++++++++++
 2019/inputs/day10       | 25 ++++++++++++++
 2019/inputs/day10-ex1   | 10 ++++++
 2019/inputs/day10-ex2   | 10 ++++++
 2019/inputs/day10-ex3   | 10 ++++++
 2019/inputs/day10-ex4   | 20 +++++++++++
 6 files changed, 148 insertions(+)
 create mode 100644 2019/day10-asteroids.py
 create mode 100644 2019/inputs/day10
 create mode 100644 2019/inputs/day10-ex1
 create mode 100644 2019/inputs/day10-ex2
 create mode 100644 2019/inputs/day10-ex3
 create mode 100644 2019/inputs/day10-ex4

diff --git a/2019/day10-asteroids.py b/2019/day10-asteroids.py
new file mode 100644
index 0000000..fe237ba
--- /dev/null
+++ b/2019/day10-asteroids.py
@@ -0,0 +1,73 @@
+from dataclasses import dataclass
+from typing import Tuple, Set
+
+
+@dataclass
+class Asteroid:
+    x: int
+    y: int
+
+    def __hash__(self):
+        return hash((self.x, self.y))
+
+    @staticmethod
+    def square_length(a: "Asteroid", b: "Asteroid"):
+        return (b.x - a.x) * (b.x - a.x) + (b.y - a.y) * (b.y - a.y)
+
+    @staticmethod
+    def cross_product(a: "Asteroid", b: "Asteroid", c: "Asteroid"):
+        return (c.y - a.y) * (b.x - a.x) - (c.x - a.x) * (b.y - a.y)
+
+    @staticmethod
+    def dot_product(a: "Asteroid", b: "Asteroid", c: "Asteroid"):
+        return (c.x - a.x) * (b.x - a.x) + (c.y - a.y) * (b.y - a.y)
+
+    @staticmethod
+    def is_between(a: "Asteroid", b: "Asteroid", c: "Asteroid"):
+        """Check if c is between a and b."""
+        cross_product = Asteroid.cross_product(a, b, c)
+
+        # compare versus epsilon for floating point values, or != 0 if using integers
+        if abs(cross_product) != 0:
+            return False
+
+        dot_product = Asteroid.dot_product(a, b, c)
+        if dot_product < 0:
+            return False
+
+        squared_length_ba = Asteroid.square_length(a, b)
+        if dot_product > squared_length_ba:
+            return False
+
+        return True
+
+    def can_see(self, other: "Asteroid", asteroids: Set["Asteroid"]) -> bool:
+        for asteroid in asteroids:
+            if asteroid in [self, other]:
+                continue
+            if Asteroid.is_between(self, other, asteroid):
+                return False
+        return True
+
+
+def main():
+    asteroids = set()
+    with open("inputs/day10") as f:
+        for y, line in enumerate(f):
+            for x, pixel in enumerate(line):
+                if pixel == "#":
+                    asteroids.add(Asteroid(x, y))
+
+    max_visible = 0
+    for source in asteroids:
+        visible = 0
+        for destination in asteroids:
+            if destination != source and source.can_see(destination, asteroids):
+                visible += 1
+        if visible > max_visible:
+            max_visible = visible
+    print(max_visible)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/2019/inputs/day10 b/2019/inputs/day10
new file mode 100644
index 0000000..eea0a46
--- /dev/null
+++ b/2019/inputs/day10
@@ -0,0 +1,25 @@
+#..#.#.#.######..#.#...##
+##.#..#.#..##.#..######.#
+.#.##.#..##..#.#.####.#..
+.#..##.#.#..#.#...#...#.#
+#...###.##.##..##...#..#.
+##..#.#.#.###...#.##..#.#
+###.###.#.##.##....#####.
+.#####.#.#...#..#####..#.
+.#.##...#.#...#####.##...
+######.#..##.#..#.#.#....
+###.##.#######....##.#..#
+.####.##..#.##.#.#.##...#
+##...##.######..##..#.###
+...###...#..#...#.###..#.
+.#####...##..#..#####.###
+.#####..#.#######.###.##.
+#...###.####.##.##.#.##.#
+.#.#.#.#.#.##.#..#.#..###
+##.#.####.###....###..##.
+#..##.#....#..#..#.#..#.#
+##..#..#...#..##..####..#
+....#.....##..#.##.#...##
+.##..#.#..##..##.#..##..#
+.##..#####....#####.#.#.#
+#..#..#..##...#..#.#.#.##
\ No newline at end of file
diff --git a/2019/inputs/day10-ex1 b/2019/inputs/day10-ex1
new file mode 100644
index 0000000..8650346
--- /dev/null
+++ b/2019/inputs/day10-ex1
@@ -0,0 +1,10 @@
+......#.#.
+#..#.#....
+..#######.
+.#.#.###..
+.#..#.....
+..#....#.#
+#..#....#.
+.##.#..###
+##...#..#.
+.#....####
\ No newline at end of file
diff --git a/2019/inputs/day10-ex2 b/2019/inputs/day10-ex2
new file mode 100644
index 0000000..dc708ab
--- /dev/null
+++ b/2019/inputs/day10-ex2
@@ -0,0 +1,10 @@
+#.#...#.#.
+.###....#.
+.#....#...
+##.#.#.#.#
+....#.#.#.
+.##..###.#
+..#...##..
+..##....##
+......#...
+.####.###.
\ No newline at end of file
diff --git a/2019/inputs/day10-ex3 b/2019/inputs/day10-ex3
new file mode 100644
index 0000000..cb09bb7
--- /dev/null
+++ b/2019/inputs/day10-ex3
@@ -0,0 +1,10 @@
+.#..#..###
+####.###.#
+....###.#.
+..###.##.#
+##.##.#.#.
+....###..#
+..#.#..#.#
+#..#.#.###
+.##...##.#
+.....#.#..
\ No newline at end of file
diff --git a/2019/inputs/day10-ex4 b/2019/inputs/day10-ex4
new file mode 100644
index 0000000..8380323
--- /dev/null
+++ b/2019/inputs/day10-ex4
@@ -0,0 +1,20 @@
+.#..##.###...#######
+##.############..##.
+.#.######.########.#
+.###.#######.####.#.
+#####.##.#.##.###.##
+..#####..#.#########
+####################
+#.####....###.#.#.##
+##.#################
+#####.##.###..####..
+..######..##.#######
+####.##.####...##..#
+.#####..#.######.###
+##...#.##########...
+#.##########.#######
+.####.#.###.###.#.##
+....##.##.###..#####
+.#.#.###########.###
+#.#.#.#####.####.###
+###.##.####.##.#..##
\ No newline at end of file