1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
|
use derive_more;
use std::io;
use std::io::prelude::*;
use std::iter;
use std::process;
use structopt::StructOpt;
#[derive(Debug, StructOpt)]
#[structopt(name = "Day 1: The Tyranny of the Rocket Equation")]
/// Calculates the fuel needed for your rocket to save Santa.
///
/// The weight of each module is read from stdin, one module weight
/// per line. See https://adventofcode.com/2019/day/1 for details.
struct Opt {
/// Includes the weight of fuel
#[structopt(short = "i", long = "include-fuel-weight")]
include_fuel_weight: bool,
}
fn main() {
let stdin = io::stdin();
let opt = Opt::from_args();
let input = stdin.lock().lines().map(|l| match l {
Ok(s) => match s.parse::<Module>() {
Ok(module) => module,
Err(e) => {
eprintln!("Invalid input \"{}\": {}", s, e);
process::exit(1);
}
},
Err(e) => {
eprintln!("Error reading input: {}", e);
process::exit(1);
}
});
println!("{}", fuel_required(input, opt.include_fuel_weight))
}
fn fuel_required(it: impl Iterator<Item = Module>, include_fuel_weight: bool) -> Fuel {
it.map(if include_fuel_weight {
Module::fuel_including_fuel_weight
} else {
Module::fuel_excluding_fuel_weight
})
.sum()
}
#[derive(Debug, derive_more::FromStr, Clone, Copy)]
struct Module {
weight: Weight,
}
impl Module {
fn fuel_excluding_fuel_weight(self) -> Fuel {
self.weight.required_fuel()
}
fn fuel_including_fuel_weight(self) -> Fuel {
iter::successors(Some(self.weight.required_fuel()), |fuel| {
if fuel.is_zero() {
None
} else {
Some(fuel.weight().required_fuel())
}
})
.sum()
}
}
#[derive(Debug, derive_more::FromStr, Clone, Copy)]
struct Weight(u32);
impl Weight {
fn required_fuel(self) -> Fuel {
Fuel((self.0 / 3).saturating_sub(2))
}
}
#[derive(Debug, derive_more::Add, derive_more::Sum, Clone, Copy, derive_more::Display)]
struct Fuel(u32);
impl Fuel {
fn weight(self) -> Weight {
Weight(self.0)
}
fn is_zero(self) -> bool {
self.0 == 0
}
}
|
