Add day 3 (bad)

2021/src/bin/day03.rs

@@ -0,0 +1,83 @@
+#![feature(test)]
+extern crate test;
+use aoc2021::common::*;
+use itertools::Itertools;
+
+const DAY: usize = 03;
+type Parsed = Vec<Vec<bool>>;
+
+fn parse_input(raw: &str) -> Parsed {
+    raw.lines().map(|line| line.chars().map(|c| c == '1').collect()).collect()
+}
+
+fn most_common(parsed: &Parsed) -> String {
+    parsed
+        .iter()
+        .skip(1)
+        .fold(parsed[0].iter().map(|&b| b as usize).collect_vec(), |acc, bits| {
+            acc.iter().zip(bits).map(|(a, &b)| a + (b as usize)).collect()
+        })
+        .into_iter()
+        .map(|b| if b as f32 >= (parsed.len() as f32) / 2.0 { '1' } else { '0' })
+        .collect()
+}
+
+fn part1(parsed: &Parsed) -> usize {
+    let gamma = most_common(parsed);
+    let epsilon: String = gamma.chars().map(|c| if c == '0' { '1' } else { '0' }).collect();
+    let gamma = usize::from_str_radix(&gamma, 2).unwrap();
+    let epsilon = usize::from_str_radix(&epsilon, 2).unwrap();
+    gamma * epsilon
+}
+
+fn part2(parsed: &Parsed) -> usize {
+    let mut matching_gamma = parsed.clone();
+    let mut matching_epsilon = parsed.clone();
+
+    for i in 0..parsed[0].len() {
+        let gamma = most_common(&matching_gamma);
+        let epsilon = most_common(&matching_epsilon);
+        let epsilon: String = epsilon.chars().map(|c| if c == '0' { '1' } else { '0' }).collect();
+        matching_gamma.retain(|n| n[i] == (gamma.chars().nth(i).unwrap() == '1'));
+        if matching_epsilon.len() > 1 {
+            matching_epsilon.retain(|n| n[i] == (epsilon.chars().nth(i).unwrap() == '1'));
+        }
+    }
+    let gamma: String = matching_gamma[0].iter().map(|&b| if b { '1' } else { '0' }).collect();
+    let epsilon: String = matching_epsilon[0].iter().map(|&b| if b { '1' } else { '0' }).collect();
+    let gamma = usize::from_str_radix(&gamma, 2).unwrap();
+    let epsilon = usize::from_str_radix(&epsilon, 2).unwrap();
+    gamma * epsilon
+}
+
+fn main() {
+    let raw = read_file(DAY);
+    let input = parse_input(&raw);
+    println!("Part 1: {}", part1(&input));
+    println!("Part 2: {}", part2(&input));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use aoc2021::*;
+
+    const TEST_INPUT: &str = "00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010";
+
+    test!(part1() == 198);
+    test!(part2() == 230);
+    bench!(part1() == 3549854);
+    bench!(part2() == 3765399);
+    bench_input!(len == 1000);
+}