Add day 2 solution.

2022/day02/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day02"
+version = "0.1.0"

2022/day02/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day02"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

2022/day02/src/main.rs

@@ -0,0 +1,58 @@
+use std::io;
+use std::io::prelude::*;
+use std::fs::File;
+
+fn read_lines(filename: &str) -> io::Result<io::Lines<io::BufReader<File>>> {
+    let file = File::open(filename)?;
+    Ok(io::BufReader::new(file).lines())
+}
+
+fn print_step(step: i8, value: u64) {
+    println!("Step {} solution: {}", step, value);
+}
+
+fn main() -> Result<(), io::Error> {
+    let mut score1: u64 = 0;
+    let mut score2: u64 = 0;
+
+    for line in read_lines("input.txt")? {
+        let text = line?;
+        let opp = parse_move(text.chars().nth(0).unwrap());
+
+        score1 += step1(opp, text.chars().nth(2).unwrap());
+        score2 += step2(opp, text.chars().nth(2).unwrap());
+    }
+
+    print_step(1, score1);
+    print_step(2, score2);
+    Ok(())
+}
+
+fn step1(opp: i8, text: char) -> u64 {
+    let me = parse_move(text);
+    return match me - opp {
+        1 | -2 => me + 6,
+        0 => me + 3,
+        -1 | 2 => me,
+        _ => panic!("Received impossible result in a match."),
+    } as u64;
+}
+
+fn step2(opp: i8, text: char) -> u64 {
+    return match text {
+        'X' => ((opp + 4) % 3) + 1,
+        'Y' => opp + 3,
+        'Z' => (opp  % 3) + 7,
+        _ => panic!("Received impossible strategy code."),
+    } as u64;
+}
+
+// Parses the second command in the input incorrectly.
+fn parse_move(x: char) -> i8 {
+    return match x {
+        'A' | 'X' => 1,
+        'B' | 'Y' => 2,
+        'C' | 'Z' => 3,
+        _ => 0,
+    };
+}