From 14306595bd1e4aa8e43e5f201e0d2c5915912383 Mon Sep 17 00:00:00 2001
From: traxys <quentin@familleboyer.net>
Date: Mon, 1 Dec 2025 14:53:20 +0100
Subject: [PATCH] Day 1

---
 src/bin/day1.rs | 96 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 src/bin/day1.rs

diff --git a/src/bin/day1.rs b/src/bin/day1.rs
new file mode 100644
index 0000000..5c6bf0e
--- /dev/null
+++ b/src/bin/day1.rs
@@ -0,0 +1,96 @@
+use std::time::Instant;
+
+use aoc_2025::{load, print_res};
+use bstr::BString;
+
+pub enum Side {
+    Plus,
+    Minus,
+}
+
+type Parsed = Vec<(Side, i16)>;
+
+#[inline(never)]
+pub fn parsing(input: &BString) -> color_eyre::Result<Parsed> {
+    core::str::from_utf8(input)?
+        .lines()
+        .map(|l| match l.as_bytes().first() {
+            None => Err(color_eyre::eyre::eyre!("Invalid empty line")),
+            Some(b'L') => Ok((Side::Minus, l[1..].parse()?)),
+            Some(b'R') => Ok((Side::Plus, l[1..].parse()?)),
+            Some(_) => Err(color_eyre::eyre::eyre!("Invalid line `{l}`")),
+        })
+        .collect()
+}
+
+#[inline(never)]
+pub fn part1(input: Parsed) {
+    let mut current: i16 = 50;
+
+    let mut zero_count = 0;
+
+    for (side, amount) in input {
+        match side {
+            Side::Plus => current += amount,
+            Side::Minus => current -= amount,
+        }
+
+        current = current.rem_euclid(100);
+        if current == 0 {
+            zero_count += 1;
+        }
+    }
+
+    print_res!("Zero count: {zero_count}");
+}
+
+#[inline(never)]
+pub fn part2(input: Parsed) {
+    let mut current: i16 = 50;
+
+    let mut zero_count = 0;
+
+    for (side, amount) in input {
+        let towards = match side {
+            Side::Plus => 1,
+            Side::Minus => -1,
+        };
+
+        for _ in 0..amount {
+            current += towards;
+
+            if current == -1 {
+                current = 99;
+            } else if current == 100 {
+                current = 0;
+            }
+
+            if current == 0 {
+                zero_count += 1;
+            }
+        }
+    }
+
+    print_res!("Zero count: {zero_count}");
+}
+
+pub fn main() -> color_eyre::Result<()> {
+    let context = load()?;
+
+    let start = Instant::now();
+    let parsed = parsing(&context.input)?;
+    let elapsed = humantime::format_duration(start.elapsed());
+
+    let start = Instant::now();
+    if context.part == 1 {
+        part1(parsed);
+    } else {
+        part2(parsed);
+    }
+    let elapsed_part = humantime::format_duration(start.elapsed());
+
+    println!("  Parsing: {elapsed}");
+    println!("  Solving: {elapsed_part}");
+
+    Ok(())
+}