Solve 2021/02

2021/day02/Cargo.lock

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

2021/day02/Cargo.toml

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+[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]

2021/day02/README.md

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+https://adventofcode.com/2021/day/2
+
+## \--- Day 2: Dive! ---
+
+Now, you need to figure out how to pilot this thing.
+
+It seems like the submarine can take a series of commands like `forward 1`,
+`down 2`, or `up 3`:
+
+  * `forward X` increases the horizontal position by `X` units.
+  * `down X` _increases_ the depth by `X` units.
+  * `up X` _decreases_ the depth by `X` units.
+
+Note that since you're on a submarine, `down` and `up` affect your _depth_ ,
+and so they have the opposite result of what you might expect.
+
+The submarine seems to already have a planned course (your puzzle input). You
+should probably figure out where it's going. For example:
+
+[code]
+
+    forward 5
+    down 5
+    forward 8
+    up 3
+    down 8
+    forward 2
+    
+[/code]
+
+Your horizontal position and depth both start at `0`. The steps above would
+then modify them as follows:
+
+  * `forward 5` adds `5` to your horizontal position, a total of `5`.
+  * `down 5` adds `5` to your depth, resulting in a value of `5`.
+  * `forward 8` adds `8` to your horizontal position, a total of `13`.
+  * `up 3` decreases your depth by `3`, resulting in a value of `2`.
+  * `down 8` adds `8` to your depth, resulting in a value of `10`.
+  * `forward 2` adds `2` to your horizontal position, a total of `15`.
+
+After following these instructions, you would have a horizontal position of
+`15` and a depth of `10`. (Multiplying these together produces `_150_`.)
+
+Calculate the horizontal position and depth you would have after following the
+planned course. _What do you get if you multiply your final horizontal
+position by your final depth?_
+
+## \--- Part Two ---
+
+Based on your calculations, the planned course doesn't seem to make any sense.
+You find the submarine manual and discover that the process is actually
+slightly more complicated.
+
+In addition to horizontal position and depth, you'll also need to track a
+third value, _aim_ , which also starts at `0`. The commands also mean
+something entirely different than you first thought:
+
+  * `down X` _increases_ your aim by `X` units.
+  * `up X` _decreases_ your aim by `X` units.
+  * `forward X` does two things:
+    * It increases your horizontal position by `X` units.
+    * It increases your depth by your aim _multiplied by_ `X`.
+
+Again note that since you're on a submarine, `down` and `up` do the opposite
+of what you might expect: "down" means aiming in the positive direction.
+
+Now, the above example does something different:
+
+  * `forward 5` adds `5` to your horizontal position, a total of `5`. Because your aim is `0`, your depth does not change.
+  * `down 5` adds `5` to your aim, resulting in a value of `5`.
+  * `forward 8` adds `8` to your horizontal position, a total of `13`. Because your aim is `5`, your depth increases by `8*5=40`.
+  * `up 3` decreases your aim by `3`, resulting in a value of `2`.
+  * `down 8` adds `8` to your aim, resulting in a value of `10`.
+  * `forward 2` adds `2` to your horizontal position, a total of `15`. Because your aim is `10`, your depth increases by `2*10=20` to a total of `60`.
+
+After following these new instructions, you would have a horizontal position
+of `15` and a depth of `60`. (Multiplying these produces `_900_`.)
+
+Using this new interpretation of the commands, calculate the horizontal
+position and depth you would have after following the planned course. _What do
+you get if you multiply your final horizontal position by your final depth?_
+

2021/day02/input/example0

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+forward 5
+down 5
+forward 8
+up 3
+down 8
+forward 2

2021/day02/src/main.rs

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+use std::env;
+use std::io::stdin;
+use std::io::BufRead;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+
+    if args.len() > 1 && args[1] == "part1" {
+        part1();
+    } else {
+        part2();
+    }
+}
+
+fn part1() {
+    let mut horizontal = 0;
+    let mut depth = 0;
+
+    for line in stdin().lock().lines() {
+        let line_result = line.unwrap();
+        let vec: Vec<&str> = line_result.split(' ').collect();
+
+        let direction = vec[0];
+        let amount: i32 = vec[1].parse().unwrap();
+
+        match direction {
+            "forward" => horizontal += amount,
+            "down" => depth += amount,
+            "up" => depth -= amount,
+            _ => (),
+        }
+
+        dbg!(direction, amount);
+    }
+
+    dbg!(horizontal, depth, horizontal * depth);
+}
+
+fn part2() {
+    let mut horizontal = 0;
+    let mut depth = 0;
+    let mut aim = 0;
+
+    for line in stdin().lock().lines() {
+        let line_result = line.unwrap();
+        let vec: Vec<&str> = line_result.split(' ').collect();
+
+        let direction = vec[0];
+        let amount: i32 = vec[1].parse().unwrap();
+
+        match direction {
+            "forward" => {
+                horizontal += amount;
+                depth += aim * amount
+            }
+            "down" => aim += amount,
+            "up" => aim -= amount,
+            _ => (),
+        }
+
+        dbg!(direction, amount);
+    }
+
+    dbg!(horizontal, depth, horizontal * depth);
+}