From e85fe2197b4ee3afe2bd0b8e90fda10ed8edc517 Mon Sep 17 00:00:00 2001
From: mirsella <mirsella@protonmail.com>
Date: Fri, 15 Dec 2023 07:12:20 +0100
Subject: [PATCH] add day15

---
 2023/Cargo.toml        |  2 +-
 2023/day15/.gitignore  | 19 ++++++++++++++
 2023/day15/Cargo.toml  | 11 ++++++++
 2023/day15/build.rs    | 28 +++++++++++++++++++++
 2023/day15/src/main.rs | 57 ++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 116 insertions(+), 1 deletion(-)
 create mode 100644 2023/day15/.gitignore
 create mode 100644 2023/day15/Cargo.toml
 create mode 100644 2023/day15/build.rs
 create mode 100644 2023/day15/src/main.rs

diff --git a/2023/Cargo.toml b/2023/Cargo.toml
index 890b19a..db661d1 100644
--- a/2023/Cargo.toml
+++ b/2023/Cargo.toml
@@ -16,7 +16,7 @@ members = [
   "day12",
   "day13",
   "day14",
-  # "day15",
+  "day15",
   # "day16",
   # "day17",
   # "day18",
diff --git a/2023/day15/.gitignore b/2023/day15/.gitignore
new file mode 100644
index 0000000..e983cca
--- /dev/null
+++ b/2023/day15/.gitignore
@@ -0,0 +1,19 @@
+input.txt
+flamegraph.svg
+perf.data*
+### Rust
+# Generated by Cargo
+# will have compiled files and executables
+debug/
+target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+
+# These are backup files generated by rustfmt
+**/*.rs.bk
+
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb
+
diff --git a/2023/day15/Cargo.toml b/2023/day15/Cargo.toml
new file mode 100644
index 0000000..c7295ee
--- /dev/null
+++ b/2023/day15/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "day15"
+authors = ["mirsella <mirsella@protonmail.com>"]
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+indexmap = "2.1.0"
+
diff --git a/2023/day15/build.rs b/2023/day15/build.rs
new file mode 100644
index 0000000..b6a19a0
--- /dev/null
+++ b/2023/day15/build.rs
@@ -0,0 +1,28 @@
+use std::fs::File;
+use std::io::{self, Read};
+use std::path::PathBuf;
+use std::{env, fs};
+
+fn replace_in_file(file_path: &PathBuf, old: &str, new: &str) -> io::Result<()> {
+    let mut contents = String::new();
+    File::open(file_path)?.read_to_string(&mut contents)?;
+    let new_contents = contents.replace(old, new);
+    if contents != new_contents {
+        println!("Updating {}", file_path.display());
+        fs::write(file_path, new_contents)?;
+    }
+    Ok(())
+}
+
+fn main() -> io::Result<()> {
+    let pkg_name = env::var("CARGO_PKG_NAME").unwrap();
+    replace_in_file(
+        &"../Cargo.toml".into(),
+        &format!("# \"{pkg_name}\""),
+        &format!("\"{pkg_name}\""),
+    )?;
+
+    replace_in_file(&"./Cargo.toml".into(), "\n[workspace]", "")?;
+
+    Ok(())
+}
diff --git a/2023/day15/src/main.rs b/2023/day15/src/main.rs
new file mode 100644
index 0000000..77b21cb
--- /dev/null
+++ b/2023/day15/src/main.rs
@@ -0,0 +1,57 @@
+use std::{collections::HashMap, ops::Index};
+
+use indexmap::IndexMap;
+
+fn hash(input: &str) -> usize {
+    input
+        .chars()
+        .fold(0, |acc, c| ((acc + c as usize) * 17) % 256)
+}
+fn part1(input: &str) -> usize {
+    input.trim().split(',').map(hash).sum()
+}
+fn part2(input: &str) -> usize {
+    let mut boxes = Vec::with_capacity(256);
+    for _ in 0..256 {
+        boxes.push(IndexMap::new())
+    }
+    for word in input.trim().split(',') {
+        let operation = word.find(['=', '-']).unwrap();
+        let (lens, value_with_del) = word.split_at(operation);
+        let value = &value_with_del[1..];
+        let h = hash(lens);
+        if word.chars().nth(operation).unwrap() == '-' {
+            boxes[h].shift_remove(lens);
+        } else {
+            boxes[h].insert(lens, value);
+        }
+    }
+    boxes
+        .iter()
+        .enumerate()
+        .map(|(boxi, h)| {
+            h.values()
+                .enumerate()
+                .map(|(p, value)| (boxi + 1) * (p + 1) * value.parse::<usize>().expect(value))
+                .sum::<usize>()
+        })
+        .sum()
+}
+fn main() {
+    let input = include_str!("../input.txt");
+    println!("Part 1: {}", part1(input));
+    println!("Part 2: {}", part2(input));
+}
+
+#[cfg(test)]
+mod tests {
+    const INPUT: &str = "rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7";
+    #[test]
+    fn part1() {
+        assert_eq!(super::part1(INPUT), 1320);
+    }
+    #[test]
+    fn part2() {
+        assert_eq!(super::part2(INPUT), 145);
+    }
+}