Added Day 2 and command line argument for specifying which day to run

rust/src/day1.rs

@@ -32,5 +32,4 @@ pub fn run() {
     assert!(calorie_totals.len() >= 3);
     println!("Day 1 Part A Answer: {}", calorie_totals[0]);
     println!("Day 1 Part B Answer: {}", calorie_totals[0] + calorie_totals[1] + calorie_totals[2]);
-
 }

rust/src/day2.rs

@@ -0,0 +1,71 @@
+use std::fs::File;
+use std::io::BufReader;
+use std::io::BufRead;
+
+pub fn run() {
+    let file = File::open("resources/day2input.txt").expect("Input file not found.");
+    let reader = BufReader::new(file);
+
+    let mut part1_score: u32 = 0;
+    let mut part2_score: u32 = 0;
+
+    for line in reader.lines() {
+        let str = line.unwrap();
+        let input_arguments = str.split(" ").collect::<Vec<&str>>();
+
+        println!("Round: {:?}, {:?}", input_arguments[0], input_arguments[1]);
+
+        let instruction_a = input_arguments[0].chars().next().unwrap();
+        let instruction_b = input_arguments[1].chars().next().unwrap();
+
+        if instruction_b == 'X' { 
+            part1_score += check_outcome(instruction_b, instruction_a) + get_shape_value(instruction_b); // rock
+            part2_score += get_shape_value(get_losing_move(instruction_a)); // lose
+        } else if instruction_b == 'Y' { 
+            part1_score += check_outcome(instruction_b, instruction_a) + get_shape_value(instruction_b); // paper
+            part2_score += 3 + get_shape_value(instruction_a); // draw
+        } else if instruction_b == 'Z' { 
+            part1_score += check_outcome(instruction_b, instruction_a) + get_shape_value(instruction_b); // scissors
+            part2_score += 6 + get_shape_value(get_winning_move(instruction_a)); // win
+        }
+    }
+
+    println!("Day 2 Part 1 Answer: {:?}", part1_score);
+    println!("Day 2 Part 2 Answer: {:?}", part2_score);
+}
+
+fn get_shape_value(shape: char) -> u32 {
+    return match shape {
+        'X' | 'A' => 1, // rock
+        'Y' | 'B' => 2, // paper
+        'Z' | 'C' => 3, // scissor
+        _ => panic!()
+    }
+}
+
+fn get_losing_move(shape: char) -> char {
+    return match shape {
+        'X' | 'A' => 'C', // rock
+        'Y' | 'B' => 'A', // paper
+        'Z' | 'C' => 'B', // scissor
+        _ => panic!()
+    } 
+}
+
+fn get_winning_move(shape: char) -> char {
+    return match shape {
+        'X' | 'A' => 'B', // rock
+        'Y' | 'B' => 'C', // paper
+        'Z' | 'C' => 'A', // scissor
+        _ => panic!()
+    } 
+}
+
+fn check_outcome(a: char, b: char) -> u32 {
+    if get_shape_value(a) == get_shape_value(b) {
+        return 3;
+    } else if get_losing_move(a) == b {
+        return 6;
+    }
+    return 0;
+}

rust/src/main.rs

@@ -1,5 +1,19 @@
+use std::env;
+
 mod day1;
+mod day2;
 
 fn main() {
-    day1::run();
+    let args: Vec<String> = env::args().collect();
+    match args.len() {
+        2 => {
+            let day_to_run = &args[1];
+            match &day_to_run[..] {
+                "day1" => day1::run(),
+                "day2" => day2::run(),
+                _ => eprintln!("error: invalid day")
+            }
+        },
+        _ => eprintln!("Error: not enough or too many arguments.")
+    };
 }