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2021: day03: use lambda for part 2

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This commit is contained in:
Antoine Martin 2021-12-03 15:44:11 +01:00
parent 1968c7894f
commit 2c0bf85249
1 changed files with 20 additions and 21 deletions
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41
aoc2021/src/day03.rs
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@ -73,12 +73,10 @@ fn part2(input: &str) -> Result<u64> {
Ok(oxygen_generator_rating * co2_scrubber_rating)
}
enum FilterStrategy {
MostCommon,
LeastCommon,
}
fn filter_by_strat(binary_numbers: &[&str], size: usize, strat: FilterStrategy) -> Result<u64> {
fn filter_by_strat<Strat>(binary_numbers: &[&str], size: usize, strat: Strat) -> Result<u64>
where
Strat: Fn(bool) -> char,
{
let mut numbers = binary_numbers.to_vec();
for pos in 0..size {
@ -87,19 +85,8 @@ fn filter_by_strat(binary_numbers: &[&str], size: usize, strat: FilterStrategy)
break;
}
let digit_of_interest = if count_ones(&numbers, pos) >= ((numbers.len() + 1) / 2) {
// majority of ones, or equality
match strat {
FilterStrategy::MostCommon => '1',
FilterStrategy::LeastCommon => '0',
}
} else {
// majority of zeroes
match strat {
FilterStrategy::MostCommon => '0',
FilterStrategy::LeastCommon => '1',
}
};
let one_is_more_common = count_ones(&numbers, pos) >= ((numbers.len() + 1) / 2);
let digit_of_interest = strat(one_is_more_common);
// TODO: use drain_filter when stable
let mut i = 0;
@ -121,14 +108,26 @@ fn filter_by_strat(binary_numbers: &[&str], size: usize, strat: FilterStrategy)
/// position, and keep only numbers with that bit in that position. If 0 and 1 are equally common,
/// keep values with a 1 in the position being considered.
fn compute_oxygen_generator_rating(binary_numbers: &[&str], size: usize) -> Result<u64> {
filter_by_strat(binary_numbers, size, FilterStrategy::MostCommon)
filter_by_strat(binary_numbers, size, |one_is_more_common| {
if one_is_more_common {
'1'
} else {
'0'
}
})
}
/// To find CO2 scrubber rating, determine the least common value (0 or 1) in the current bit
/// position, and keep only numbers with that bit in that position. If 0 and 1 are equally
/// common, keep values with a 0 in the position being considered.
fn compute_co2_scrubber_rating(binary_numbers: &[&str], size: usize) -> Result<u64> {
filter_by_strat(binary_numbers, size, FilterStrategy::LeastCommon)
filter_by_strat(binary_numbers, size, |one_is_more_common| {
if one_is_more_common {
'0'
} else {
'1'
}
})
}
#[cfg(test)]