rust experiments

decode.rs

/*
Given the mapping a = 1, b = 2, ... z = 26, and an encoded message, count the number of ways it can be decoded.

For example, the message '111' would give 3, since it could be decoded as 'aaa', 'ka', and 'ak'.

You can assume that the messages are decodable. For example, '001' is not allowed.
 */

use std::collections::HashMap;
use std::rc;

fn count_times<'a>(msg: &'a str, cache: &'a HashMap<&'a str, i32>) -> i32 {
    match cache.get(msg) {
        Some(result) => *result,
        None => {
          let len = msg.len();
          let result = match len {
              0 => 1,
              1 => if &msg[..1] == "0" { 0 } else { 1 },
              _ => {
                  let mut total = 0;
                  let mut val: i32 = msg[..1].parse().unwrap();
                  if val > 0 {
                      total += count_times(&msg[1..], &cache);
                  }
                  val = msg[..2].parse().unwrap();
                  if 0 < val && val <= 26 {
                      total += count_times(&msg[2..], &cache);
                  }
                  total
              }
          };
          cache.clone().insert(msg, result);
          result
        }
    }
}

fn main() {
    let msg = String::from("111");
    let cache = rc::Rc::new(HashMap::new());
    println!("{:?}", count_times(&msg, &cache));
}