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2023: Day 6, part 2

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Wesley Moore 2023-12-06 17:58:31 +10:00
parent f202587c42
commit 87c5a2c02c
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1 changed files with 26 additions and 4 deletions
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30
2023/day6/src/main.rs
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@ -9,11 +9,11 @@ fn main() -> Result<(), BoxError> {
.ok_or("missing input file path")?; .ok_or("missing input file path")?;
let input = fs::read_to_string(input_path)?; let input = fs::read_to_string(input_path)?;
let mut lines = input.lines(); let mut lines = input.lines();
let times = lines.next().ok_or("missing times")?; let times_text = lines.next().ok_or("missing times")?;
let distances = lines.next().ok_or("missing distances")?; let distances_text = lines.next().ok_or("missing distances")?;
let times = parse("Time:", times)?; let times = parse("Time:", times_text)?;
let distances = parse("Distance:", distances)?; let distances = parse("Distance:", distances_text)?;
if times.len() != distances.len() { if times.len() != distances.len() {
return Err("time/distance length mismatch".into()); return Err("time/distance length mismatch".into());
} }
@ -36,6 +36,20 @@ fn main() -> Result<(), BoxError> {
println!("Part 1: {}", results.iter().fold(1, |a, b| a * b)); println!("Part 1: {}", results.iter().fold(1, |a, b| a * b));
let time = parse_part2("Time:", times_text)?;
let record_distance = parse_part2("Distance:", distances_text)?;
let mut result = 0;
(1..time - 1).for_each(|hold| {
let velocity = hold;
let distance = (time - hold) * velocity;
if distance > record_distance {
result += 1;
}
});
println!("Part 2: {result}");
Ok(()) Ok(())
} }
@ -52,3 +66,11 @@ fn parse(prefix: &str, line: &str) -> Result<Vec<usize>, BoxError> {
.collect::<Result<Vec<_>, _>>()?; .collect::<Result<Vec<_>, _>>()?;
Ok(numbers) Ok(numbers)
} }
fn parse_part2(_prefix: &str, line: &str) -> Result<usize, BoxError> {
line.chars()
.filter(|c| c.is_ascii_digit())
.collect::<String>()
.parse()
.map_err(BoxError::from)
}