add 2023/15/02

2023/src/bin/day15.rs

@@ -3,32 +3,51 @@ extern crate test;
 use aoc2023::{boilerplate, common::*};
 
 const DAY: usize = 15;
-type I = u32;
+type I = usize;
 type Parsed<'a> = impl Iterator<Item = &'a str> + Clone;
 
 fn parse_input(raw: &str) -> Parsed {
     raw.trim_end_matches('\n').split(',')
 }
 
-fn hash(s: &str) -> I {
-    s.bytes().fold(0, |acc, b| (acc + b as I) * 17 & 255)
+fn hash(s: &[u8]) -> I {
+    s.iter().fold(0, |acc, &b| (acc + b as I) * 17 & 255)
 }
 
 fn part1(parsed: &Parsed) -> I {
-    parsed.clone().map(hash).inspect(|n| println!("{n}")).sum()
+    parsed.clone().map(|s| hash(s.as_bytes())).sum()
 }
 
 fn part2(parsed: &Parsed) -> I {
-    unimplemented!()
+    let mut boxes: Vec<Vec<(&[u8], u8)>> = vec![vec![]; 256];
+    for s in parsed.clone() {
+        match s.as_bytes() {
+            [label @ .., b'-'] => {
+                let hash = hash(&label);
+                if let Some(p) = boxes[hash].iter().position(|(l, _)| l == &label) {
+                    boxes[hash].remove(p);
+                }
+            }
+            [label @ .., b'=', focal_strength] => {
+                let hash = hash(&label);
+                match boxes[hash].iter().position(|(l, _)| l == &label) {
+                    Some(p) => boxes[hash][p] = (&label, focal_strength - b'0'),
+                    None => boxes[hash].push((&label, focal_strength - b'0')),
+                }
+            }
+            _ => unreachable!(),
+        }
+    }
+    boxes.into_iter().zip(1..).flat_map(|(b, i)| b.into_iter().zip(1..).map(move |((_, f), j)| i * j * f as I)).sum()
 }
 
 boilerplate! {
     TEST_INPUT == "rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7"
     for tests: {
         part1: { TEST_INPUT => 1320 },
-        part2: { TEST_INPUT => 0 },
+        part2: { TEST_INPUT => 145 },
     },
     bench1 == 510273,
-    bench2 == 0,
+    bench2 == 212449,
     bench_parse: |i: &Parsed| i.clone().count() => 4000,
 }