chore: don't compute sqrt for no good reason

Author: clechasseur

aoclp/src/positioning/pt_3d.rs

@@ -184,13 +184,13 @@ where
     (a.x - b.x).abs() + (a.y - b.y).abs() + (a.z - b.z).abs()
 }
 
-/// Returns the [Euclidian distance] between two points in 3D space.
+/// Returns the square of the [Euclidian distance] between two points in 3D space.
 ///
 /// [Euclidian distance]: https://en.wikipedia.org/wiki/Euclidean_distance
-pub fn euclidian<T>(a: Pt3d<T>, b: Pt3d<T>) -> f64
+pub fn euclidian_squared<T>(a: Pt3d<T>, b: Pt3d<T>) -> T
 where
-    T: NumCast,
+    T: Signed + Clone,
 {
-    let (a, b) = (a.cast::<f64>(), b.cast::<f64>());
-    ((a.x - b.x).abs().powi(2) + (a.y - b.y).abs().powi(2) + (a.z - b.z).abs().powi(2)).sqrt()
+    let (x, y, z) = ((a.x - b.x).abs(), (a.y - b.y).abs(), (a.z - b.z).abs());
+    (x.clone() * x) + (y.clone() * y) + (z.clone() * z)
 }

aoclp_solutions/src/y2025/day_08.rs

@@ -1,7 +1,7 @@
 use std::collections::HashMap;
 
 use aoclp::num::Zero;
-use aoclp::positioning::pt_3d::{euclidian, Pt3d};
+use aoclp::positioning::pt_3d::{euclidian_squared, Pt3d};
 use aoclp::solvers_impl::input::safe_get_input_as_many;
 use itertools::Itertools;
 
@@ -29,8 +29,8 @@ fn circuits(all: bool) -> (HashMap<Pt3d, usize>, HashMap<usize, usize>, (Pt3d, P
     boxes
         .into_iter()
         .array_combinations()
-        .map(|[a, b]| (a, b, euclidian(a, b)))
-        .sorted_unstable_by(|(_, _, a), (_, _, b)| a.partial_cmp(b).unwrap())
+        .map(|[a, b]| (a, b, euclidian_squared(a, b)))
+        .sorted_unstable_by_key(|(_, _, d)| *d)
         .take(if all { 1_000_000 } else { 1_000 })
         .for_each(|(a, b, _)| match (circuits.get(&a).copied(), circuits.get(&b).copied()) {
             (Some(a_id), Some(b_id)) if a_id == b_id => (),