Advent of Code day 12

day12.rs

extern crate serde; // 0.6.6
extern crate serde_json; // 0.6.0

use std::fs::File;
use std::io::BufReader;
use serde_json::Value as Value;

fn sum_numbers(json: &Value) -> i64 {
    match *json {
        Value::I64(n) => n as i64,
        Value::U64(n) => n as i64,
        Value::Array(ref vec) => vec.iter().fold(0, |acc, ref item| acc + sum_numbers(&item)),
        Value::Object(ref map) => {
            let has_red = map.values().any({|x| match *x {
                Value::String(ref s) if s == "red" => true,
                _ => false,
            }});
            if has_red {
                return 0;
            }

            map.values().fold(0, |acc, ref item| acc + sum_numbers(&item))
        }
        serde_json::Value::F64(n) => panic!("Unexpected float {}", n),
        _ => 0,
    }
}

fn main() {
    let input_fname = "day12_input.txt";
    let f = File::open(input_fname).unwrap();
    let json: Value = serde_json::from_reader(BufReader::new(f)).unwrap();
    println!("Result: {}", sum_numbers(&json));
}