day15

1 files changed, 84 insertions, 0 deletions

diff --git a/2023/day15.rs b/2023/day15.rs
new file mode 100644
index 0000000..5c6bde7
--- /dev/null
+++ b/2023/day15.rs
@@ -0,0 +1,84 @@
+#![allow(dead_code)]
+#![allow(unused_variables)]
+#![allow(unused_mut)]
+use std::fs::File;
+use std::io::Read;
+
+fn hash(s: &str) -> usize {
+    let mut h: usize = 0;
+
+    for b in s.bytes() {
+        h = ((h + (b as usize)) * 17) % 256;
+    }
+    h
+}
+
+#[derive(Debug, PartialEq, Clone)]
+struct Lens {
+    name: String,
+    h: usize,
+    f: Option<usize>,
+}
+
+fn main() {
+    // let filename = "in/day15.ref";
+    let filename = "in/day15.pzl";
+
+    let mut f = File::open(filename).expect("cannot open file");
+    let mut content = String::new();
+    f.read_to_string(&mut content).expect("cannot read file");
+    let token = content.trim_end().split(',');
+
+    let mut ls: Vec<Lens> = Vec::new();
+    let mut res1: usize = 0;
+    for t in token {
+        res1 += hash(t);
+
+        if t.contains('=') {
+            let (n, f) = t.split_once('=').unwrap();
+            ls.push(Lens {
+                name: n.to_owned(),
+                h: hash(n),
+                f: Some(f.parse().unwrap()),
+            });
+        } else {
+            let n = t.trim_end_matches('-');
+            ls.push(Lens {
+                name: n.to_owned(),
+                h: hash(n),
+                f: None,
+            });
+        }
+    }
+
+    let mut hm: Vec<Vec<Lens>> = vec![[].to_vec(); 256];
+    for l in ls {
+        if let Some(f) = l.f {
+            let mut found = false;
+            for ll in 0..hm[l.h].len() {
+                if hm[l.h][ll].name == l.name {
+                    hm[l.h][ll].f = l.f;
+                    found = true;
+                    break;
+                }
+            }
+            if !found {
+                hm[l.h].push(l);
+            }
+        } else {
+            hm[l.h].retain(|x| x.name != l.name);
+        }
+    }
+
+    let mut res2 = 0;
+    for b in 0..hm.len() {
+        for l in 0..hm[b].len() {
+            res2 += (b + 1) * (l + 1) * hm[b][l].f.unwrap();
+        }
+    }
+
+    println!("res1: {}", res1);
+    println!("res2: {}", res2);
+    assert_eq!(res1, 506437);
+    assert_eq!(res2, 288521);
+}