Complete day 3

Cargo.lock

@@ -27,3 +27,11 @@ dependencies = [
  "anyhow",
  "common",
 ]
+
+[[package]]
+name = "day03"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "common",
+]

crates/day03/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "day03"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0"
+common = { path = "../common" }

crates/day03/src/input/test.txt

@@ -0,0 +1,12 @@
+00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010

crates/day03/src/main.rs

@@ -0,0 +1,108 @@
+use anyhow::{anyhow, Result};
+use common::instrument;
+
+const INPUT: &str = include_str!("input/input.txt");
+
+fn get_most_common(lines: &[&str]) -> Vec<usize> {
+    let mut most_common = vec![0; lines[0].len()];
+
+    for line in lines.iter() {
+        let chars = line.chars();
+        for (i, c) in chars.enumerate() {
+            if c == '1' {
+                most_common[i] += 1;
+            }
+        }
+    }
+
+    return most_common;
+}
+
+fn solve_part1(input: &str) -> Result<i32> {
+    let lines: Vec<&str> = input.trim().lines().collect();
+
+    let most_common = get_most_common(&lines);
+
+    let mut gamma = 0;
+    let mut epsilon = 0;
+    for (i, c) in most_common.into_iter().enumerate() {
+        if i > 0 {
+            gamma <<= 1;
+            epsilon <<= 1;
+        }
+        if c > (lines.len() / 2) {
+            gamma |= 1;
+        } else {
+            epsilon |= 1;
+        }
+    }
+
+    Ok(gamma * epsilon)
+}
+
+fn solve_part2(input: &str) -> Result<i32> {
+    let lines: Vec<&str> = input.trim().lines().collect();
+
+    let mut oxygen = lines.clone();
+    let mut co2 = lines.clone();
+
+    for i in 0..lines[0].len() {
+        let oxygen_most_common = get_most_common(&oxygen);
+        let co2_most_common = get_most_common(&co2);
+
+        if oxygen.len() > 1 {
+            if oxygen_most_common[i] as f32 >= (oxygen.len() as f32 / 2.0) {
+                oxygen = oxygen
+                    .into_iter()
+                    .filter(|l| l.chars().nth(i).unwrap() == '1')
+                    .collect();
+            } else {
+                oxygen = oxygen
+                    .into_iter()
+                    .filter(|l| l.chars().nth(i).unwrap() == '0')
+                    .collect();
+            }
+        }
+
+        if co2.len() > 1 {
+            if co2_most_common[i] as f32 >= (co2.len() as f32 / 2.0) {
+                co2 = co2
+                    .into_iter()
+                    .filter(|l| l.chars().nth(i).unwrap() == '0')
+                    .collect();
+            } else {
+                co2 = co2
+                    .into_iter()
+                    .filter(|l| l.chars().nth(i).unwrap() == '1')
+                    .collect();
+            }
+        }
+
+        if oxygen.len() == 1 && co2.len() == 1 {
+            return Ok(i32::from_str_radix(oxygen[0], 2)? * i32::from_str_radix(co2[0], 2)?);
+        }
+    }
+
+    Err(anyhow!("No ratings found"))
+}
+
+fn main() {
+    instrument!(solve_part1(INPUT).unwrap(), solve_part2(INPUT).unwrap());
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const TEST_INPUT: &str = include_str!("input/test.txt");
+
+    #[test]
+    fn solves_part1() {
+        assert_eq!(solve_part1(TEST_INPUT).unwrap(), 198);
+    }
+
+    #[test]
+    fn solves_part2() {
+        assert_eq!(solve_part2(TEST_INPUT).unwrap(), 230);
+    }
+}