Added year directories for advent of code

advent_of_code/2021/d2/src/main.rs

@@ -0,0 +1,64 @@
+use std::io::{self, BufRead};
+use std::path::Path;
+use std::fs::File;
+
+fn main(){
+    println!("Advent of Code #2!\n");
+
+    let path = Path::new("./2.txt");
+    let display = path.display();
+
+    let file = match File::open(&path) {
+        Err(why) => panic!("Couldn't open {}: {}", display, why),
+        Ok(file) => file,
+    };
+
+    let lines = io::BufReader::new(file).lines();
+    let mut instructions = Vec::<(String, u32)>::new();
+
+    for line in lines {
+        if let Ok(l) = line {
+            let mut words_iter = l.split_whitespace();
+            let direction = words_iter.next().unwrap().to_string();
+            let distance = words_iter.next().unwrap().parse::<u32>().unwrap();
+
+            instructions.push((direction, distance));
+        }
+    }
+
+    let mut depth = 0;
+    let mut position = 0;
+    for (direction, distance) in &instructions {
+        match direction.as_str() {
+            "forward" => position += distance,
+            "up" => depth -= distance,
+            "down" => depth += distance,
+            s => println!("Stumbled upon unknown input: {}", s),
+        }
+    }
+
+    println!("Position of {} * depth of {} equals {}", position, depth, position * depth);
+
+    
+    // Now for the second part of day 2
+    // So instead of just adding to the depth immediately through the up and down commands, we now use
+    // a so-called aim
+
+    depth = 0;
+    position = 0;
+    let mut aim = 0;
+
+    for (direction, distance) in &instructions {
+        match direction.as_str() {
+            "forward" => {
+                depth += aim * distance;
+                position += distance
+            },
+            "up" => aim -= distance,
+            "down" => aim += distance,
+            s => println!("Stumbled upon unknown input: {}", s),
+        }
+    }
+
+    println!("Position of {} * depth of {} equals {}", position, depth, position * depth);
+}