day8: avoid floats for performance

src/day8.rs

@@ -1,25 +1,26 @@
-use std::{f64, fmt::Display};
+use std::fmt::Display;
 
 use aoc_runner_derive::{aoc, aoc_generator};
 use itertools::Itertools;
 
 #[derive(PartialEq, Clone, Debug)]
 struct Junction {
-    pos: (f64, f64, f64),
+    pos: (i64, i64, i64),
 }
 
-fn distance(a: &Junction, b: &Junction) -> f64 {
+fn squared_distance(a: &Junction, b: &Junction) -> u64 {
     if a.pos == b.pos {
-        0f64
+        0
     } else {
-        ((a.pos.0 - b.pos.0).powi(2) + (a.pos.1 - b.pos.1).powi(2) + (a.pos.2 - b.pos.2).powi(2))
-            .sqrt()
+        (a.pos.0 - b.pos.0).pow(2) as u64
+            + (a.pos.1 - b.pos.1).pow(2) as u64
+            + (a.pos.2 - b.pos.2).pow(2) as u64
     }
 }
 
 impl Junction {
-    fn distance(&self, other: &Junction) -> f64 {
-        distance(self, other)
+    fn squared_distance(&self, other: &Junction) -> u64 {
+        squared_distance(self, other)
     }
 }
 
@@ -93,8 +94,8 @@ fn part1_impl(input: &Circuits, n: usize) -> u64 {
         .iter()
         .enumerate()
         .tuple_combinations()
-        .map(|((a_pos, a), (b_pos, b))| (a_pos, b_pos, a.distance(b)))
-        .sorted_unstable_by(|a, b| a.2.partial_cmp(&b.2).unwrap())
+        .map(|((a_pos, a), (b_pos, b))| (a_pos, b_pos, a.squared_distance(b)))
+        .sorted_unstable_by_key(|(_a_pos, _b_pos, d)| *d)
         .take(n)
     {
         circuits.connect(a, b)
@@ -125,8 +126,8 @@ fn part2(input: &Circuits) -> u64 {
         .iter()
         .enumerate()
         .tuple_combinations()
-        .map(|((a_pos, a), (b_pos, b))| (a_pos, b_pos, a.distance(b)))
-        .sorted_unstable_by(|a, b| a.2.partial_cmp(&b.2).unwrap())
+        .map(|((a_pos, a), (b_pos, b))| (a_pos, b_pos, a.squared_distance(b)))
+        .sorted_unstable_by_key(|(_a_pos, _b_pos, d)| *d)
     {
         circuits.connect(a, b);
         if circuits.circuits.len() == 1 {