pub fn day3() {
    // let input = r#"
    // 00100
    // 11110
    // 10110
    // 10111
    // 10101
    // 01111
    // 00111
    // 11100
    // 10000
    // 11001
    // 00010
    // 01010
    //     "#;
    let input = include_str!("../input/day3.txt");

    let numbers: Vec<u32> = input
        .trim()
        .lines()
        .map(|l| u32::from_str_radix(l.trim(), 2).unwrap())
        .collect();
    let nbits = input.trim().lines().next().unwrap().trim().len();

    let gamma = gamma(&numbers);
    println!("gamma: {}", gamma);
    println!("epsilon: {}", epsilon(gamma, nbits));

    println!("oxygen: {}", oxygen(&numbers, nbits));
    println!("co2: {}", co2(&numbers, nbits));
}

fn gamma(numbers: &[u32]) -> u32 {
    let mut gamma: u32 = 0;
    for i in 0..32 {
        gamma = gamma | (most_common_bit(numbers, i) << i);
    }
    gamma
}

fn most_common_bit(numbers: &[u32], pos: u32) -> u32 {
    let count = numbers.iter().filter(|&n| (n >> pos) & 1 == 1).count();
    let frac = (count as f32) / (numbers.len() as f32);
    frac.round() as u32
}

fn epsilon(gamma: u32, nbits: usize) -> u32 {
    println!("{:#b}", !gamma);
    println!("{:#b}", 2_u32.pow(nbits as u32) - 1);
    !gamma & ((1 << nbits) - 1)
}

fn oxygen(numbers: &[u32], nbits: usize) -> u32 {
    let mut vec: Vec<u32> = numbers.into();
    let mut bit: u32 = nbits as u32;
    while vec.len() != 1 {
        bit -= 1;
        let most_common = most_common_bit(&vec, bit);
        vec = vec
            .into_iter()
            .filter(|n| ((n >> bit) & 1) == most_common)
            .collect();
        for n in vec.iter() {
            print!("{:#b}, ", n);
        }
        println!();
    }
    *vec.get(0).unwrap()
}

fn co2(numbers: &[u32], nbits: usize) -> u32 {
    let mut vec: Vec<u32> = numbers.into();
    let mut bit: u32 = nbits as u32;
    while vec.len() != 1 {
        bit -= 1;
        let least_common = 1 - most_common_bit(&vec, bit);
        vec = vec
            .into_iter()
            .filter(|n| ((n >> bit) & 1) == least_common)
            .collect();
        // for n in vec.iter() {
        //     print!("{:#b}, ", n);
        // }
        // println!();
    }
    *vec.get(0).unwrap()
}