From ed00f1e3c63c51fa923534d0a11d59bda48f88fa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9o=20LUDWIG?= <contact@theoludwig.fr>
Date: Fri, 9 Feb 2024 08:48:14 +0100
Subject: [PATCH] perf: improve day 8 - part 1

---
 day_8/src/lib.rs | 60 +++++++++++++++++++-----------------------------
 1 file changed, 24 insertions(+), 36 deletions(-)

diff --git a/day_8/src/lib.rs b/day_8/src/lib.rs
index ffa83cc..584f458 100644
--- a/day_8/src/lib.rs
+++ b/day_8/src/lib.rs
@@ -4,7 +4,7 @@ use std::collections::HashMap;
 #[derive(Debug, Default, PartialEq, Eq, Clone)]
 pub struct DesertMap {
     pub directions: Vec<HorizontalDirection>,
-    pub nodes: HashMap<String, (String, String)>,
+    pub nodes: HashMap<String, [String; 2]>,
 }
 
 impl FromStr for DesertMap {
@@ -33,9 +33,9 @@ impl FromStr for DesertMap {
     /// let expected_result = DesertMap {
     ///     directions: vec![HorizontalDirection::Right, HorizontalDirection::Left],
     ///     nodes: HashMap::from([
-    ///         (String::from("AAA"), (String::from("BBB"), String::from("CCC"))),
-    ///         (String::from("BBB"), (String::from("DDD"), String::from("EEE"))),
-    ///         (String::from("CCC"), (String::from("ZZZ"), String::from("GGG"))),
+    ///         (String::from("AAA"), [String::from("BBB"), String::from("CCC")]),
+    ///         (String::from("BBB"), [String::from("DDD"), String::from("EEE")]),
+    ///         (String::from("CCC"), [String::from("ZZZ"), String::from("GGG")]),
     ///    ])
     /// };
     ///
@@ -58,10 +58,10 @@ impl FromStr for DesertMap {
                 .unwrap_or_default()
                 .replace(['(', ')'], "");
             let mut values_line = values_line.split(", ");
-            let value = (
+            let value = [
                 values_line.next().unwrap_or_default().to_string(),
                 values_line.next().unwrap_or_default().to_string(),
-            );
+            ];
             result.nodes.insert(key.to_string(), value);
         }
         Ok(result)
@@ -71,8 +71,14 @@ impl FromStr for DesertMap {
 #[derive(Debug, Default, PartialEq, Eq, Copy, Clone)]
 pub enum HorizontalDirection {
     #[default]
-    Left,
-    Right,
+    Left = 0,
+    Right = 1,
+}
+
+impl HorizontalDirection {
+    pub const fn index(&self) -> usize {
+        *self as usize
+    }
 }
 
 impl From<char> for HorizontalDirection {
@@ -89,39 +95,21 @@ const KEY_START: &str = "AAA";
 const KEY_END: &str = "ZZZ";
 
 pub fn part_1(input: &str) -> usize {
-    let desert_map = DesertMap::from_str(input).unwrap_or_default();
+    let mut desert_map = DesertMap::from_str(input).unwrap_or_default();
     let mut steps = 0;
     let mut current_step_key = KEY_START.to_string();
-    let mut current_direction_index: usize = 0;
-
     while current_step_key != KEY_END {
-        let current_direction = desert_map
-            .directions
-            .get(current_direction_index)
-            .cloned()
-            .unwrap_or_else(|| {
-                current_direction_index = 0;
-                desert_map
-                    .directions
-                    .get(current_direction_index)
-                    .cloned()
-                    .unwrap_or_default()
-            });
-
-        let current_step_value = desert_map
-            .nodes
-            .get(&current_step_key)
-            .cloned()
-            .unwrap_or_default();
-        current_step_key = match current_direction {
-            HorizontalDirection::Left => current_step_value.0.clone(),
-            HorizontalDirection::Right => current_step_value.1.clone(),
-        };
-
-        current_direction_index += 1;
+        let direction_index = steps % desert_map.directions.len();
+        let current_direction = &desert_map.directions[direction_index];
+        let current_step_value =
+            if let Some(step_value) = desert_map.nodes.get_mut(&current_step_key) {
+                step_value
+            } else {
+                break;
+            };
+        current_step_key = current_step_value[current_direction.index()].to_string();
         steps += 1;
     }
-
     steps
 }