From 0f17084f181b2b99931cd24745bf7a4af0c5c3db Mon Sep 17 00:00:00 2001
From: Johannes <jschaef@mail.uni-paderborn.de>
Date: Wed, 11 Dec 2019 18:07:39 +0100
Subject: [PATCH] day10 task 1

---
 input/day10.txt    | 29 ++++++++++++++++++++++++-----
 src/tasks/day10.rs | 38 +++++++++++++++++++++-----------------
 2 files changed, 45 insertions(+), 22 deletions(-)

diff --git a/input/day10.txt b/input/day10.txt
index 6a9f2d1..bf4ecf6 100644
--- a/input/day10.txt
+++ b/input/day10.txt
@@ -1,5 +1,24 @@
-.#..#
-.....
-#####
-....#
-...##
\ No newline at end of file
+##.##..#.####...#.#.####
+##.###..##.#######..##..
+..######.###.#.##.######
+.#######.####.##.#.###.#
+..#...##.#.....#####..##
+#..###.#...#..###.#..#..
+###..#.##.####.#..##..##
+.##.##....###.#..#....#.
+########..#####..#######
+##..#..##.#..##.#.#.#..#
+##.#.##.######.#####....
+###.##...#.##...#.######
+###...##.####..##..#####
+##.#...#.#.....######.##
+.#...####..####.##...##.
+#.#########..###..#.####
+#.##..###.#.######.#####
+##..##.##...####.#...##.
+###...###.##.####.#.##..
+####.#.....###..#.####.#
+##.####..##.#.##..##.#.#
+#####..#...####..##..#.#
+.##.##.##...###.##...###
+..###.########.#.###..#.
\ No newline at end of file
diff --git a/src/tasks/day10.rs b/src/tasks/day10.rs
index dec8ed3..33edd15 100644
--- a/src/tasks/day10.rs
+++ b/src/tasks/day10.rs
@@ -21,7 +21,7 @@ fn task1(asteroids: &HashSet<(i32, i32)>) {
     let max = asteroids
         .iter()
         .map(|asteroid| {
-            //println!("inspecting {:?}", asteroid);
+            println!("inspecting {:?}", asteroid);
             // map to number of other asteroids it sees
             let mut others = asteroids.clone();
             others.remove(&asteroid);
@@ -29,11 +29,15 @@ fn task1(asteroids: &HashSet<(i32, i32)>) {
             let count = others
                 .iter()
                 .filter(|target| {
-                    !others
+                    let blocker = others
                         .iter()
-                        .any(|occluder| blocks_view(*asteroid, **target, *occluder))
+                        .find(|occluder| blocks_view(*asteroid, **target, **occluder));
+                    if let Some(occluder) = blocker {
+                        println!("{:?} -> X{:?}X -> {:?}", asteroid, occluder, target);
+                    }
+                    !blocker.is_some()
                 })
-                //.inspect(|target| println!("sees {:?}", target))
+                .inspect(|target| println!("sees {:?}", target))
                 .count();
             println!("{:?}: {}", asteroid, count);
             count
@@ -43,29 +47,29 @@ fn task1(asteroids: &HashSet<(i32, i32)>) {
     println!(
         "Task 1: maximum visible asteroids from another asteroid are {}",
         max
-    ); //283 too high, 257 too low
+    );
 }
 
 fn blocks_view(pov: (i32, i32), target: (i32, i32), occluder: (i32, i32)) -> bool {
-    let ux = occluder.0 - pov.0;
-    let uy = occluder.1 - pov.1;
-
-    let sx = (target.0 - pov.0) as f32 / ux as f32;
-    let sy = (target.1 - pov.1) as f32 / uy as f32;
-    //dbg!((ux, uy, sx, sy));
-    match (ux, uy) {
-        (0, _) => sy.abs() > 1.0 && target.0 == pov.0,
-        (_, 0) => sx.abs() > 1.0 && target.1 == pov.1,
-        (_, _) => sx.abs() > 1.0 && sx == sy,
+    if occluder == target {
+        return false;
     }
+    fn d(a: (i32, i32), b: (i32, i32)) -> f32 {
+        ((a.0 - b.0) as f32).powi(2) + ((a.1 - b.1) as f32).powi(2).sqrt()
+    }
+    // using polar coordinates
+    let alpha_occluder = ((occluder.1 - pov.1) as f32).atan2((occluder.0 - pov.0) as f32);
+    let alpha_target = ((target.1 - pov.1) as f32).atan2((target.0 - pov.0) as f32);
+    (alpha_occluder - alpha_target).abs() <= std::f32::EPSILON && d(pov, target) > d(pov, occluder)
 }
 
 mod test {
     #[test]
     fn block_test() {
         assert_eq!(true, super::blocks_view((3, 4), (1, 0), (2, 2)));
-        assert_ne!(true, super::blocks_view((3, 4), (2, 2), (1, 0)));
-        assert_ne!(true, super::blocks_view((3, 4), (1, 0), (1, 2)));
+        assert_eq!(false, super::blocks_view((3, 4), (2, 2), (1, 0)));
+        assert_eq!(false, super::blocks_view((3, 4), (1, 0), (1, 2)));
         assert_eq!(true, super::blocks_view((4, 4), (4, 0), (4, 3)));
+        assert_eq!(false, super::blocks_view((3, 2), (1, 0), (4, 3)));
     }
 }