56 lines
1.8 KiB
Rust
56 lines
1.8 KiB
Rust
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#[macro_use]
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extern crate lazy_static;
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extern crate regex;
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use regex::Regex;
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use std::fs::File;
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use std::io::{BufRead, BufReader};
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use std::iter::Iterator;
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fn calc_remaining_monomers(polymers: &str) -> usize {
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lazy_static! {
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static ref POLYMER: Regex = Regex::new(r"aA|Aa|bB|Bb|cC|Cc|dD|Dd|eE|Ee|fF|Ff|gG|Gg|hH|Hh|iI|Ii|jJ|Jj|kK|Kk|lL|Ll|mM|Mm|nN|Nn|oO|Oo|pP|Pp|qQ|Qq|rR|Rr|sS|Ss|tT|Tt|uU|Uu|vV|Vv|wW|Ww|xX|Xx|yY|Yy|zZ|Zz").unwrap();
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}
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if POLYMER.is_match(polymers) {
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calc_remaining_monomers(&POLYMER.replace_all(polymers, ""))
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} else {
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polymers.len()
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}
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}
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fn calc_most_significant_monomer(polymers: &str) {
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let chars: Vec<char> = (b'a' ..= b'z').map(char::from).collect();
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let mut min_letter = 'a';
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let mut min_length = polymers.len();
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for mychar in chars.iter() {
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let regex_str = format!(r"{}|{}", mychar, mychar.to_uppercase());
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let r = Regex::new(regex_str.as_str()).unwrap();
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let new_len = react_monomer(polymers, r);
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if new_len < min_length {
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min_letter = *mychar;
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min_length = new_len;
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}
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}
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println!("minimum new length {} found by replacing {}", min_length, min_letter);
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}
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fn react_monomer(polymers: &str, r: Regex) -> usize {
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if r.is_match(polymers) {
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react_monomer(&r.replace_all(polymers, ""), r)
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} else {
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calc_remaining_monomers(polymers)
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}
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}
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fn main() {
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let lines: Vec<String> = BufReader::new(File::open("input").unwrap())
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.lines()
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.map(|line| line.unwrap())
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.collect();
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let polymers = lines.get(0).unwrap().as_str();
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let reacted_len = calc_remaining_monomers(polymers);
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println!("remaining polymers has size {}", reacted_len);
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calc_most_significant_monomer(polymers);
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}
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