#![feature(is_sorted)] use itertools::Itertools; pub fn main() { let (lower, upper) = (172_930, 683_082); let valid_part1 = (lower..upper) .map(|n| n.to_string().chars().collect::>()) .filter(|n| n.is_sorted()) .filter(|v| v.clone().iter().dedup().count() != v.len()); println!("Part 1: {}", valid_part1.clone().count()); let part2 = valid_part1 .filter(|vec| { vec.iter() .group_by(move |n| *n) .into_iter() .filter_map(|(_, v)| if v.count() == 2 { Some(true) } else { None }) // can’t do this because I’m too smol brained for the borrow checker //.filter(|(_, v)| v.count() == 2) .count() > 0 }) .count(); println!("Part 2: {}", part2); }