2019/rust/day01/src/main.rs


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use std::io::{self, BufRead};

fn read_input() -> Vec<i32> {
    let stdin = io::stdin();
    let nums: Vec<i32> = stdin.lock().lines().map(|x| x.unwrap().parse().unwrap()).collect();
    nums
}

fn first_puzzle(payloads:&Vec<i32>) -> i32 {
    let fuel = payloads.iter().fold(0, |fuel, mass| fuel + mass/3-2);

    fuel
}

fn second_puzzle(payloads:&Vec<i32>) -> i32 {
    fn fuel_required(mass:&i32) -> i32 {
        let fuel = mass/3-2;

        if fuel > 0 {
            fuel + fuel_required(&fuel)
        } else {
            0
        }
    }

    let fuel = payloads.iter().fold(0, |fuel, mass| fuel + fuel_required(mass));
    fuel
}

fn main() {
    let payloads = read_input();

    let first = first_puzzle(&payloads);
    println!("first: {}", first);

    let second = second_puzzle(&payloads);
    println!("second: {}", second);
}