From bf4be8d233ccd0b79be21cc26295cff1b83f8038 Mon Sep 17 00:00:00 2001
From: Tobias Marschner <contact@tobiasm.dev>
Date: Sun, 11 Feb 2024 04:43:54 +0100
Subject: [PATCH] Solution for 2022/day03-part2

---
 2022/day03-part2/Cargo.toml  |  8 ++++++++
 2022/day03-part2/src/main.rs | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)
 create mode 100644 2022/day03-part2/Cargo.toml
 create mode 100644 2022/day03-part2/src/main.rs

diff --git a/2022/day03-part2/Cargo.toml b/2022/day03-part2/Cargo.toml
new file mode 100644
index 0000000..d0ac9ff
--- /dev/null
+++ b/2022/day03-part2/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "day03-part2"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/2022/day03-part2/src/main.rs b/2022/day03-part2/src/main.rs
new file mode 100644
index 0000000..f86a5d1
--- /dev/null
+++ b/2022/day03-part2/src/main.rs
@@ -0,0 +1,35 @@
+use std::collections::HashSet;
+
+fn main() {
+    // Use command line arguments to specify the input filename.
+    let args: Vec<String> = std::env::args().collect();
+    if args.len() < 2 {
+        panic!("Usage: ./main <input-file>\nNo input file provided. Exiting.");
+    }
+
+    // Next, read the contents of the input file into a string for easier processing.
+    let input = std::fs::read_to_string(&args[1]).expect("Error opening file");
+    // Line-by-line processing is easiest.
+    let mut input = input.lines();
+
+    // --- TASK BEGIN ---
+    let mut total = 0;
+    while let Some(line) = input.next() {
+        // Read the next three lines and turn them into HashSets.
+        let first: HashSet<char> = line.chars().collect();
+        let second: HashSet<char> = input.next().unwrap().chars().collect();
+        let third: HashSet<char> = input.next().unwrap().chars().collect();
+        // Use set intersection to determine the item that's common to all three sets.
+        let item = *first.intersection(&second).copied().collect::<HashSet<char>>().intersection(&third).next().unwrap();
+        // Calculate the priority.
+        let priority = match item {
+            item if item.is_ascii_lowercase() => (item as u32) - ('a' as u32) + 1,
+            item if item.is_ascii_uppercase() => (item as u32) - ('A' as u32) + 27,
+            _ => {panic!("Character out of range")}
+        };
+        // Accumulate the priorities.
+        total += priority;
+    }
+    println!("Total priority: {total}");
+}
+