and p2

2024/04/p2/main.rs

@@ -0,0 +1,86 @@
+use std::{
+    cmp,
+    fs::File,
+    io::Read,
+    time::{Duration, Instant},
+};
+
+fn main() -> std::io::Result<()> {
+    let args: Vec<_> = std::env::args().collect();
+    let filename = &args[1];
+    let runs: u32 = args[2]
+        .parse()
+        .expect("did not receive a number as `runs` argument");
+
+    let mut contents = vec![];
+    let mut file = File::open(filename)?;
+    file.read_to_end(&mut contents)?;
+    let lines: Vec<_> = contents.split(|&b| b == b'\n').collect();
+
+    let mut max = Duration::ZERO;
+    let mut avg = Duration::ZERO;
+    let mut min = Duration::MAX;
+    let result = run(&lines);
+    for i in 0..runs {
+        let a = Instant::now();
+        let run_result = run(&lines);
+        let b = Instant::now();
+        if result != run_result {
+            panic!(
+                "supposed result is {} but this run got {} after {} runs",
+                result, run_result, i
+            );
+        }
+
+        let d = b - a;
+        max = cmp::max(d, max);
+        min = cmp::min(d, min);
+        avg += d / runs;
+    }
+
+    println!("\x1b[0;34mtotal \x1b[1;33m{result}\x1b[0;34m\n  runs  \x1b[1;33m{runs:?}\x1b[0;34m\n  avg.  \x1b[1;35m{avg:?}\x1b[0;34m\n  max.  \x1b[1;31m{max:?}\x1b[0;34m\n  min.  \x1b[1;32m{min:?}\x1b[0m");
+    Ok(())
+}
+
+fn run(lines: &[&[u8]]) -> usize {
+    let mut t = 0;
+    for (i, ln) in lines.iter().enumerate() {
+        'l: for (j, &ch) in ln.iter().enumerate() {
+            if ch == b'A' {
+                let mut passes = true;
+                for chars in [(1, -1), (1, 1)].iter().map(|(y, x)| {
+                    (
+                        getdat(lines, (j, i), (*x, *y)),
+                        getdat(lines, (j, i), (-*x, -*y)),
+                    )
+                }) {
+                    let (Some(a), Some(b)) = chars else { continue 'l; };
+                    if !((a == b'M' && b == b'S') || (a == b'S' && b == b'M')) {
+                        passes = false;
+                        break;
+                    }
+                }
+                if passes { t += 1; }
+            }
+        }
+    }
+    t
+}
+
+macro_rules! pstve_try_none {
+    ($a:expr, $b:expr) => {{
+        let r = $a + $b;
+        if r < 0 {
+            return None;
+        }
+        r
+    }};
+}
+
+fn getdat(buf: &[&[u8]], pos: (usize, usize), dir: (isize, isize)) -> Option<u8> {
+    let new_1 = pstve_try_none!(pos.1 as isize, dir.1) as usize;
+    let new_0 = pstve_try_none!(pos.0 as isize, dir.0) as usize;
+    let ln = buf.get(new_1)?;
+    let ch = ln.get(new_0)?;
+    Some(*ch)
+}