58 lines
1.5 KiB
Rust
58 lines
1.5 KiB
Rust
#![warn(clippy::pedantic)]
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use std::io::{stdin, BufRead};
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fn find_rating(num_bits: usize, mut range: &[usize], keep_most_common_bit: bool) -> usize {
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for idx in (0..num_bits).rev() {
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if range.len() == 1 {
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break;
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}
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let nth_bit = |x| x >> idx & 1;
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let partition_point = range.iter().position(|&n| nth_bit(n) == 1).unwrap();
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let center_bit = nth_bit(range[range.len() / 2]);
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let keep_first_half = if keep_most_common_bit {
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center_bit == 0
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} else {
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center_bit == 1
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};
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if keep_first_half {
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range = &range[..partition_point];
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} else {
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range = &range[partition_point..];
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}
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}
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range[0]
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}
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fn main() {
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let lines: Vec<_> = stdin().lock().lines().map(Result::unwrap).collect();
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let num_bits = lines[0].len();
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let gamma: usize = (0..num_bits)
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.map(|i| {
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lines
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.iter()
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.filter(|line| line.chars().nth(i).unwrap() == '1')
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.count()
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})
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.map(|n| if n > lines.len() / 2 { 1 } else { 0 })
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.reduce(|accum, bit| accum << 1 | bit)
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.unwrap();
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let sigma = !gamma & ((1 << num_bits) - 1);
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println!("{}", gamma * sigma);
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let mut numbers: Vec<_> = lines
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.iter()
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.map(|n| usize::from_str_radix(n, 2).unwrap())
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.collect();
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numbers.sort_unstable();
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let oxygen = find_rating(num_bits, &numbers, true);
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let co2 = find_rating(num_bits, &numbers, false);
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println!("{}", oxygen * co2);
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}
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