From 4729fa062dff30d848a1a5376ca0017163b9d886 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Christian=20Gr=C3=BCnhage?=
 <jan.christian@gruenhage.xyz>
Date: Sat, 4 Dec 2021 11:47:22 +0100
Subject: [PATCH] implement day 3

---
 src/day_03.rs | 107 ++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs    |   1 +
 2 files changed, 108 insertions(+)
 create mode 100644 src/day_03.rs

diff --git a/src/day_03.rs b/src/day_03.rs
new file mode 100644
index 0000000..92af10a
--- /dev/null
+++ b/src/day_03.rs
@@ -0,0 +1,107 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+
+#[aoc_generator(day3)]
+pub fn parse_diagnostics(input: &str) -> Vec<String> {
+    input.lines().map(String::from).collect()
+}
+
+#[aoc(day3, part1)]
+pub fn calculate_power_consumption(input: &[String]) -> usize {
+    let gamma_factor = most_common_bit_string(input);
+    let epsilon_factor = invert_binary_string(&gamma_factor);
+    let gamma_factor = usize::from_str_radix(&gamma_factor, 2).unwrap();
+    let epsilon_factor = usize::from_str_radix(&epsilon_factor, 2).unwrap();
+    gamma_factor * epsilon_factor
+}
+
+pub fn most_common_bit(input: &[String], pos: usize) -> char {
+    let mut count = 0;
+    for val in input {
+        if val.get(pos..=pos).unwrap() == "1" {
+            count += 1
+        }
+    }
+    if count * 2 >= input.len() {
+        '1'
+    } else {
+        '0'
+    }
+}
+
+pub fn most_common_bit_string(input: &[String]) -> String {
+    let mut ret_val = String::new();
+    for i in 0..input[0].len() {
+        ret_val.push(most_common_bit(input, i))
+    }
+    ret_val
+}
+
+pub fn invert_binary_string(val: &str) -> String {
+    let mut ret_val = String::new();
+    for charactor in val.chars() {
+        match charactor {
+            '0' => ret_val.push('1'),
+            '1' => ret_val.push('0'),
+            _ => (),
+        }
+    }
+    ret_val
+}
+
+pub fn get_oxygen_generator_rating(input: &[String]) -> usize {
+    get_recursive_prefix_match(input, false)
+}
+
+pub fn get_co2_scrubber_rating(input: &[String]) -> usize {
+    get_recursive_prefix_match(input, true)
+}
+
+pub fn get_recursive_prefix_match(input: &[String], invert: bool) -> usize {
+    let mut input = Vec::from(input);
+    for i in 0..input[0].len() {
+        if input.len() > 1 {
+            let mut target = String::from(most_common_bit(&input, i));
+            if invert {
+                target = invert_binary_string(&target);
+            }
+            input.retain(|val| val.get(i..=i) == Some(&target));
+        } else {
+            break;
+        }
+    }
+    assert_eq!(input.len(), 1);
+    usize::from_str_radix(&input[0], 2).unwrap()
+}
+
+#[aoc(day3, part2)]
+pub fn calculate_life_support_rating(input: &[String]) -> usize {
+    get_oxygen_generator_rating(input) * get_co2_scrubber_rating(input)
+}
+
+#[cfg(test)]
+mod test {
+    const EXAMPLE_INPUT: &str = "00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010";
+
+    #[test]
+    fn test_power_consumption_example() {
+        let result = super::calculate_power_consumption(&super::parse_diagnostics(EXAMPLE_INPUT));
+        assert_eq!(result, 198);
+    }
+
+    #[test]
+    fn test_life_support_example() {
+        let result = super::calculate_life_support_rating(&super::parse_diagnostics(EXAMPLE_INPUT));
+        assert_eq!(result, 230);
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 43d3e05..6b0f086 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,5 +2,6 @@ use aoc_runner_derive::aoc_lib;
 
 pub mod day_01;
 pub mod day_02;
+pub mod day_03;
 
 aoc_lib! { year = 2021 }