From dc97d6fe01ca7afd2618540f9a4470b6a3849674 Mon Sep 17 00:00:00 2001
From: Justin Wernick <justin@worthe-it.co.za>
Date: Fri, 15 Dec 2023 09:01:19 +0200
Subject: Day 15 part 1

---
 2023/src/bin/day_15.rs | 44 ++++++++++++++++++++++++++++++++++++--------
 1 file changed, 36 insertions(+), 8 deletions(-)

(limited to '2023/src')

diff --git a/2023/src/bin/day_15.rs b/2023/src/bin/day_15.rs
index b3a610b..badb34f 100644
--- a/2023/src/bin/day_15.rs
+++ b/2023/src/bin/day_15.rs
@@ -1,19 +1,47 @@
-use nom::IResult;
 use std::fs;
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let input = fs::read_to_string("inputs/day_2.txt")?;
-    let parsed = Example::parser(&input).unwrap().1;
-    dbg!(&parsed);
+    let input = fs::read_to_string("inputs/day_15.txt")?;
+    let parsed = InitializationInstructions::parse(&input);
+    dbg!(&parsed.hash_sum());
 
     Ok(())
 }
 
 #[derive(Debug)]
-struct Example;
+struct InitializationInstructions(Vec<String>);
 
-impl Example {
-    fn parser(_input: &str) -> IResult<&str, Self> {
-        todo!()
+impl InitializationInstructions {
+    fn parse(input: &str) -> Self {
+        Self(input.trim().split(",").map(|s| s.to_owned()).collect())
     }
+
+    fn hash_sum(&self) -> u32 {
+        self.0.iter().map(|s| hash(&s)).sum()
+    }
+}
+
+fn hash(input: &str) -> u32 {
+    let mut result: u32 = 0;
+    for c in input.bytes() {
+        result += Into::<u32>::into(c);
+        result *= 17;
+        result %= 256;
+    }
+    result
+}
+
+#[test]
+fn examples() {
+    assert_eq!(hash("rn=1"), 30);
+    assert_eq!(hash("cm-"), 253);
+    assert_eq!(hash("qp=3"), 97);
+    assert_eq!(hash("cm=2"), 47);
+    assert_eq!(hash("qp-"), 14);
+    assert_eq!(hash("pc=4"), 180);
+    assert_eq!(hash("ot=9"), 9);
+    assert_eq!(hash("ab=5"), 197);
+    assert_eq!(hash("pc-"), 48);
+    assert_eq!(hash("pc=6"), 214);
+    assert_eq!(hash("ot=7"), 231);
 }
-- 
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