add timekeeping, also day1 that got left out somehow

2021/src/day1.rs

@@ -0,0 +1,31 @@
+use color_eyre::eyre;
+
+use crate::lib::ParseLines;
+
+
+fn run(data: &str) -> eyre::Result<()> {
+    let mut single_increases = 0;
+    let mut window_increases = 0;
+    let mut prev = (None, None, None);
+    for res in data.parse_lines::<i32>() {
+        let n = res?;
+        if let Some(p) = prev.2 {
+            // apparently we can't combine "if let" and regular boolean conditions
+            if n > p {
+                single_increases += 1;
+            }
+        }
+
+        if let (Some(first), Some(second), Some(third)) = prev {
+            if (n + second + third) > (first + second + third) {
+                window_increases += 1;
+            }
+        }
+        // would have forgotten this if not for the warning triggered by "let mut" without mutation
+        prev = (prev.1, prev.2, Some(n));
+    }
+
+    println!("One: {}", single_increases);
+    println!("Two: {}", window_increases);
+    Ok(())
+}

2021/src/main.rs

@@ -1,14 +1,30 @@
+use std::time::{Instant};
+
 use color_eyre::eyre;
 
 mod lib;
 use lib::load;
-
 mod day2;
 
 
-
-
 fn main() -> eyre::Result<()> {
     let data = load("data/02.txt")?;
-    day2::run(&data)
+    let start = Instant::now();
+    day2::run(&data)?;
+    let (dur, unit) = format_ns(start.elapsed().as_nanos());
+    println!("Completed in {}{}", dur, unit);
+    Ok(())
+}
+
+
+fn format_ns(ns: u128) -> (u128, &'static str) {
+    const UNITS: [&str; 4] = ["ns", "us", "ms", "s"];
+    let mut display_n = ns;
+    let mut unit_idx = 0;
+    while display_n > 1000 && unit_idx < 4 {
+        display_n /= 1000;
+        unit_idx += 1
+    }
+
+    (display_n, UNITS[unit_idx])
 }