Day 2

src/bin/day2.rs

@@ -0,0 +1,86 @@
+use core::str;
+use std::{cmp, time::Instant};
+
+use aoc_2024::{load, print_res};
+use bstr::BString;
+
+pub struct Report(Vec<u64>);
+
+type Parsed = Vec<Report>;
+
+pub fn parsing(input: &BString) -> color_eyre::Result<Parsed> {
+    str::from_utf8(input)?
+        .lines()
+        .map(|l| {
+            Ok(Report(
+                l.split_ascii_whitespace()
+                    .map(|x| -> color_eyre::Result<u64> { Ok(x.parse()?) })
+                    .collect::<Result<_, _>>()?,
+            ))
+        })
+        .collect()
+}
+
+impl Report {
+    fn is_safe(&self, mut can_dampen: bool) -> bool {
+        assert!(self.0.len() >= 2);
+
+        let cmp = self.0[0].cmp(&self.0[1]);
+        if cmp == cmp::Ordering::Equal {
+            return false;
+        }
+
+        for window in self.0.windows(2) {
+            if cmp != window[0].cmp(&window[1]) {
+                if can_dampen {
+                    can_dampen = false;
+                } else {
+                    return false;
+                }
+            }
+
+            if window[0].abs_diff(window[1]) > 3 {
+                if can_dampen {
+                    can_dampen = false;
+                } else {
+                    return false;
+                }
+            }
+        }
+
+        true
+    }
+}
+
+pub fn part1(input: Parsed) {
+    let safe_count = input.iter().filter(|x| x.is_safe(false)).count();
+
+    print_res!("There are {safe_count} safe reports");
+}
+
+pub fn part2(input: Parsed) {
+    let safe_count = input.iter().filter(|x| x.is_safe(true)).count();
+
+    print_res!("There are {safe_count} safe reports with the dampener");
+}
+
+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(())
+}