add: p2, ioncare anymor

2025/08/p2.rs

@@ -0,0 +1,89 @@
+#![feature(linked_list_cursors)]
+use std::{collections::HashSet, ptr::from_mut};
+
+pub type Coords = (usize, usize, usize);
+
+#[unsafe(no_mangle)]
+pub extern "Rust" fn challenge_usize(buf: &[u8]) -> usize {
+    let ln_iter = buf[..(buf.len() - 1)].split(|&b| b == b'\n');
+
+    let mut circuits: Vec<HashSet<Coords>> = Vec::new();
+
+    for ln in ln_iter {
+        let this_box = parse_jbox_ln(ln);
+        circuits.push(HashSet::new());
+        circuits.last_mut().unwrap().insert(this_box);
+    }
+
+    let mut prev_mul = None;
+    while let Some(this_mul) = merge_shortest_pair(&mut circuits) {
+        prev_mul = Some(this_mul);
+    }
+
+    prev_mul.expect("not a single merge was done")
+}
+
+fn distance(b1: Coords, b2: Coords) -> usize {
+    let a = b1.0 - b2.0;
+    let b = b1.1 - b2.1;
+    let c = b1.2 - b2.2;
+
+    (a * a + b * b + c * c).isqrt()
+}
+
+fn merge_shortest_pair(from: &mut Vec<HashSet<Coords>>) -> Option<usize> {
+    let mut min = None;
+
+    for (i, circ) in unsafe { &mut *std::ptr::from_mut(from) }
+        .iter_mut()
+        .enumerate()
+    {
+        let raw_circ = from_mut(circ);
+
+        for &coor in circ.iter() {
+            let rest_slice = &mut from[(i + 1)..];
+            for other_circ in rest_slice.iter_mut() {
+                let raw_other_circ = from_mut(other_circ);
+
+                for &coor2 in other_circ.iter() {
+                    let dist = distance(coor, coor2);
+
+                    match min {
+                        Some((min_dist, _, _, _, _)) => {
+                            if min_dist > dist && dist != 0 {
+                                min =
+                                    Some((dist, raw_circ, raw_other_circ, coor2, coor.0 * coor2.0));
+                            }
+                        }
+                        None => {
+                            min = Some((dist, raw_circ, raw_other_circ, coor2, coor.0 * coor2.0));
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    if let Some((_, circ1, circ2, coor, that_mul)) = min {
+        let (circ1, circ2) = (unsafe { &mut *circ1 }, unsafe { &mut *circ2 });
+        circ1.insert(coor);
+        circ2.remove(&coor);
+        Some(that_mul)
+    } else {
+        None
+    }
+}
+
+fn parse_jbox_ln(ln: &[u8]) -> Coords {
+    let mut iter = ln.split(|&b| b == b',').map(|num_bytes| {
+        num_bytes
+            .iter()
+            .fold(0, |acc, b| acc * 10 + ((*b - b'0') as usize))
+    });
+
+    (
+        iter.next().unwrap(),
+        iter.next().unwrap(),
+        iter.next().unwrap(),
+    )
+}