main.rs

use std::collections::HashSet;
use std::fs::File;
use std::io::prelude::*;

fn main() {
    /* let rooms = "aaaaa-bbb-z-y-x-123[abxyz]
a-b-c-d-e-f-g-h-987[abcde]
not-a-real-room-404[oarel]
totally-real-room-200[decoy]";
*/
    let mut file = File::open("data.txt").unwrap();
    let mut string = String::new();
    file.read_to_string(&mut string).unwrap();
    let rooms = string;
    let total_value: usize = rooms.split('\n').map(value).sum();
    println!("Total value is {}", total_value);
}

fn value(name: &str) -> usize {
    if name == "" { return 0 };
    let start: &str = &name[..name.find(char::is_numeric).unwrap()];
    //println!("Start: {:?}", start);
    let mut char_dedup_vec = start.chars().filter(|&c| c != '-').collect::<HashSet<char>>().into_iter().collect::<Vec<char>>();
    char_dedup_vec.sort();
    char_dedup_vec.sort_by_key(|&k| start.len()-start.matches(k).count());
    let true_checksum: String = char_dedup_vec.into_iter().take(5).collect();
    let claimed_checksum = &name[name.len()-6..name.len()-1];
    //println!("True checksum: {:?}, claimed checksum: {:?}", true_checksum, claimed_checksum);
    let id: usize = name.matches(char::is_numeric).collect::<String>().parse().unwrap();
    //println!("Id: {}", id);
    if true_checksum == claimed_checksum {
        let decrypted = start.chars().map(|x| shift(x, id)).collect::<String>();
        if decrypted.matches("north").count() > 0 {
            println!("Decryped: {}", decrypted);
            id
        } else {
            0
        }
    } else {
        0
    }
}

fn shift(c: char, amount: usize) -> char {
    match c {
        '-' => ' ',
        'a' ... 'z' => {
            let base = 'a' as usize;
            let ord = c as usize - base;
            let shifted_ord = (ord + amount) % 26;
            (shifted_ord + base) as u8 as char
        },
        _ => panic!("Unexpected character input to shift: {}", c),
    }
}