From 2f467ae7d783f2d0649a285dafab7d20018e6481 Mon Sep 17 00:00:00 2001
From: "max.nuding" <max.nuding@uni-konstanz.de>
Date: Fri, 9 Dec 2022 08:59:08 +0100
Subject: [PATCH] Improve follow_head function

---
 src/day09/mod.rs | 26 +++++++-------------------
 1 file changed, 7 insertions(+), 19 deletions(-)

diff --git a/src/day09/mod.rs b/src/day09/mod.rs
index 34bc8e3..a258086 100644
--- a/src/day09/mod.rs
+++ b/src/day09/mod.rs
@@ -35,27 +35,15 @@ impl Position {
     }
 
     pub fn follow_head(&self, head: &Position) -> Self {
-        if head.x == self.x && head.y > self.y + 1 {
-            self.move_down()
-        } else if head.x == self.x && head.y < self.y - 1 {
-            self.move_up()
-        } else if head.x > self.x + 1 && head.y == self.y {
-            self.move_right()
-        } else if head.x < self.x - 1 && head.y == self.y {
-            self.move_left()
-        } else if (head.x - self.x).abs() == 1 && (head.y - self.y).abs() == 1 {
-            // One away diagonally - don't move
+        // Based on jenarvaezg/aoc2022
+        // https://old.reddit.com/r/adventofcode/comments/zgnice/2022_day_9_solutions/izi6s4p/
+        if self.x.abs_diff(head.x) < 2 && self.y.abs_diff(head.y) < 2 {
             self.clone()
-        } else if head.x < self.x && head.y < self.y {
-            self.move_left().move_up()
-        } else if head.x > self.x && head.y < self.y {
-            self.move_right().move_up()
-        } else if head.x > self.x && head.y > self.y {
-            self.move_right().move_down()
-        } else if head.x < self.x && head.y > self.y {
-            self.move_left().move_down()
         } else {
-            self.clone()
+            Self {
+                x: self.x + (head.x - self.x).signum(),
+                y: self.x + (head.y - self.y).signum(),
+            }
         }
     }
 }