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static DAY: u8 = 6;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", possible_ways(&input));
println!("{DAY}b: {}", possible_ways_single_race(&input));
}
fn count_ways(time: u64, record: u64) -> u64 {
let mut ways = 0;
for hold_button in 1 .. time {
let moving_time = time - hold_button;
let boat_distance = moving_time * hold_button;
if boat_distance > record {
ways += 1;
}
}
ways
}
fn possible_ways(input: &[String]) -> u64 {
let get_numbers = |x: &str| {
x.split_once(':').unwrap().1.to_string()
.split(' ')
.filter(|s| !s.is_empty())
.map(|s| s.parse().unwrap())
.collect::<Vec<u64>>()
};
let times = get_numbers(&input[0]);
let distances = get_numbers(&input[1]);
times.iter()
.zip(distances.iter())
.map(|(time, distance)| count_ways(*time, *distance))
.product()
}
fn possible_ways_single_race(input: &[String]) -> u64 {
let get_number = |mut x: String| -> u64 {
x.retain(|c| c.is_ascii_digit());
x.parse().unwrap()
};
let time = get_number(input[0].clone());
let distance = get_number(input[1].clone());
count_ways(time, distance)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"Time: 7 15 30",
"Distance: 9 40 200",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(possible_ways(&input), 288);
assert_eq!(possible_ways_single_race(&input), 71503);
}
}
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