From 9b09b974ebc8773444b93843a3a3c6d43384867b Mon Sep 17 00:00:00 2001
From: Stefan Schwarz <ssz@bitsbeats.com>
Date: Wed, 13 May 2020 00:53:12 +0200
Subject: [PATCH] remove non-astroids from map

---
 src/day10/main.rs | 75 +++++++++++++++++++----------------------------
 1 file changed, 30 insertions(+), 45 deletions(-)

diff --git a/src/day10/main.rs b/src/day10/main.rs
index 9366ac0..2269e31 100644
--- a/src/day10/main.rs
+++ b/src/day10/main.rs
@@ -1,4 +1,3 @@
-use std::cmp::Ordering;
 use std::collections::{HashMap, HashSet};
 use std::fs::File;
 use std::io::{BufRead, BufReader};
@@ -46,18 +45,6 @@ impl Sub for &XY {
     }
 }
 
-impl PartialOrd for XY {
-    fn partial_cmp(&self, other: &XY) -> Option<Ordering> {
-        self.angle().partial_cmp(&other.angle())
-    }
-}
-
-impl Ord for XY {
-    fn cmp(&self, other: &XY) -> Ordering {
-        self.angle().partial_cmp(&other.angle()).unwrap()
-    }
-}
-
 impl XY {
     fn direction(&self) -> Self {
         let d = gcd(self.y, self.x).abs();
@@ -88,20 +75,17 @@ impl XY {
 }
 
 struct MonitoringStation {
-    map: HashMap<XY, Position>,
+    map: Vec<XY>,
 }
 
 impl MonitoringStation {
     fn laser(&self, root: &XY, skip: usize, n: usize) -> Vec<XY> {
-        let mut map: HashMap<XY, Vec<XY>> = HashMap::new();
+        let mut map: HashMap<XY, Vec<&XY>> = HashMap::new();
         // collect vec for each direction
         map = self
             .map
             .iter()
-            .filter_map(|(xy, pos)| {
-                if *pos == Position::Empty {
-                    return None;
-                }
+            .filter_map(|xy| {
                 if xy == root {
                     return None;
                 }
@@ -109,7 +93,7 @@ impl MonitoringStation {
                 Some((xy, rel.direction()))
             })
             .fold(map, |mut acc, (xy, dir)| {
-                acc.entry(dir).or_insert(vec![]).push(xy.clone());
+                acc.entry(dir).or_insert(vec![]).push(xy);
                 acc
             });
 
@@ -122,8 +106,9 @@ impl MonitoringStation {
 
         // lets iterate over sorted angles
         let mut angles = map.keys().cloned().collect::<Vec<XY>>();
-        angles.sort();
+        angles.sort_by(|a, b| a.angle().partial_cmp(&b.angle()).unwrap());
 
+        // cycle around and return first element of each vec
         angles
             .iter()
             .cycle()
@@ -140,23 +125,21 @@ impl MonitoringStation {
             .flatten()
             .skip(skip)
             .take(n)
+            .cloned()
             .collect::<Vec<XY>>()
     }
 
     fn find(&self) -> (usize, XY) {
-        let best = (0, XY::from((0, 0)));
-        self.map
+        let best = (0, &XY::from((0, 0)));
+        let best = self
+            .map
             .iter()
-            .filter(|(_, pos)| **pos == Position::Astroid)
-            .map(|(root, _)| {
+            .map(|root| {
                 let insight = self
                     .map
                     .iter()
                     // get direction to any of the astroids
-                    .filter_map(|(xy, pos)| {
-                        if *pos == Position::Empty {
-                            return None;
-                        }
+                    .filter_map(|xy| {
                         let rel = xy - root;
                         Some(rel.direction())
                     })
@@ -169,12 +152,17 @@ impl MonitoringStation {
                     - 1;
                 (insight, root)
             })
-            .fold(best, |acc, astroid| {
-                if astroid.0 > acc.0 {
-                    return (astroid.0, astroid.1.clone());
-                }
-                acc
-            })
+            .fold(
+                best,
+                |acc, astroid| {
+                    if astroid.0 > acc.0 {
+                        astroid
+                    } else {
+                        acc
+                    }
+                },
+            );
+        (best.0, best.1.clone())
     }
 }
 
@@ -183,25 +171,22 @@ where
     T: BufRead,
 {
     fn from(reader: T) -> Self {
-        let map: HashMap<XY, Position> = HashMap::new();
         let map = reader
             .split(b'\n')
             .enumerate()
             .flat_map(|(y, line)| {
                 line.unwrap()
-                    .iter()
+                    .into_iter()
                     .enumerate()
-                    .map(|(x, c)| {
+                    .filter_map(move |(x, c)| {
                         let xy = XY::from((x, y));
-                        let p = Position::from(c);
-                        (xy, p)
+                        match Position::from(&c) {
+                            Position::Astroid => Some(xy),
+                            Position::Empty => None,
+                        }
                     })
-                    .collect::<Vec<(XY, Position)>>()
             })
-            .fold(map, |mut map, (xy, p)| {
-                map.insert(xy.clone(), p.clone());
-                map
-            });
+            .collect::<Vec<XY>>();
         MonitoringStation { map }
     }
 }