From 282ed1aa2e8827fe5a19206c5654db1e97b2f29d Mon Sep 17 00:00:00 2001
From: Stephen Waits <steve@waits.net>
Date: Wed, 1 Dec 2021 22:55:12 -0700
Subject: [PATCH] day2 solution

---
 data/day02-test.txt |    6 +
 data/day02.txt      | 1000 +++++++++++++++++++++++++++++++++++++++++++
 src/day02.rs        |   61 +++
 src/main.rs         |    2 +
 4 files changed, 1069 insertions(+)
 create mode 100644 data/day02-test.txt
 create mode 100644 data/day02.txt
 create mode 100644 src/day02.rs

diff --git a/data/day02-test.txt b/data/day02-test.txt
new file mode 100644
index 0000000..b7172ac
--- /dev/null
+++ b/data/day02-test.txt
@@ -0,0 +1,6 @@
+forward 5
+down 5
+forward 8
+up 3
+down 8
+forward 2
diff --git a/data/day02.txt b/data/day02.txt
new file mode 100644
index 0000000..d61291a
--- /dev/null
+++ b/data/day02.txt
@@ -0,0 +1,1000 @@
+forward 2
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diff --git a/src/day02.rs b/src/day02.rs
new file mode 100644
index 0000000..df4a9d3
--- /dev/null
+++ b/src/day02.rs
@@ -0,0 +1,61 @@
+use crate::utils::read_file;
+use anyhow::Result;
+
+fn parse_line(s: &str) -> (&str, i32) {
+    let parsed: Vec<&str> = s.splitn(2, ' ').collect();
+    let instruction = parsed[0];
+    let quantity = parsed[1].parse::<i32>().unwrap();
+    (instruction, quantity)
+}
+
+fn follow_course(s: &str) -> i32 {
+    let (mut pos, mut depth) = (0, 0);
+    s.lines().for_each(|line| match parse_line(line) {
+        ("forward", d) => pos += d,
+        ("down", d) => depth += d,
+        ("up", d) => depth -= d,
+        _ => unreachable!(),
+    });
+    pos * depth
+}
+
+fn follow_course_better(s: &str) -> i32 {
+    let (mut pos, mut depth, mut aim) = (0, 0, 0);
+    s.lines().for_each(|line| match parse_line(line) {
+        ("forward", d) => {
+            pos += d;
+            depth += aim * d;
+        }
+        ("down", d) => aim += d,
+        ("up", d) => aim -= d,
+        _ => unreachable!(),
+    });
+    pos * depth
+}
+
+pub(crate) fn run() -> Result<(usize, usize)> {
+    let input = read_file("data/day02.txt")?;
+    Ok((
+        follow_course(&input) as usize,
+        follow_course_better(&input) as usize,
+    ))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_example() {
+        let input = read_file("data/day02-test.txt").unwrap();
+        assert_eq!(follow_course(&input), 150);
+        assert_eq!(follow_course_better(&input), 900);
+    }
+
+    #[test]
+    fn test_my_data() {
+        let input = read_file("data/day02.txt").unwrap();
+        assert_eq!(follow_course(&input), 2070300);
+        assert_eq!(follow_course_better(&input), 2078985210);
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 05bf281..0f4ae56 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,9 +1,11 @@
 use anyhow::Result;
 
 mod day01;
+mod day02;
 mod utils;
 
 fn main() -> Result<()> {
     println!("day01: {:?}", day01::run()?);
+    println!("day02: {:?}", day02::run()?);
     Ok(())
 }