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
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
|
use {
anyhow::{
anyhow,
Context,
Result,
},
std::{
collections::BTreeMap,
env::args,
fs::File,
io::{
BufRead,
BufReader,
},
path::Path,
},
};
fn read_input<T: AsRef<Path>>(filename: T) -> Result<Vec<usize>> {
let reader = BufReader::new(File::open(filename)?);
reader.lines().next().ok_or(anyhow!(""))??.split(',').map(
|s| {
let n = s.parse()?;
Ok(n)
}
).collect()
}
fn part1<'a, I: Copy + IntoIterator<Item = &'a usize>>(input: I) -> Result<usize> {
let mut subs: BTreeMap<usize, usize> = BTreeMap::new();
let mut fuel = 0;
for position in input {
*subs.entry(*position).or_insert(0) += 1;
}
while subs.len() > 1 {
let first_position = *subs.keys().next().ok_or(anyhow!("Couldn't get first position."))?;
let last_position = *subs.keys().rev().next()
.ok_or(anyhow!("Couldn't get last position."))?;
let first_value = *subs.get(&first_position).ok_or(anyhow!("Couldn't get first value."))?;
let last_value = *subs.get(&last_position).ok_or(anyhow!("Couldn't get last value."))?;
if first_value <= last_value {
let value = subs.remove(&first_position)
.ok_or(anyhow!("Couldn't remove first value"))?;
let new_position = first_position + 1;
*subs.entry(new_position).or_insert(0) += value;
fuel += value;
}
if first_value >= last_value {
let value = subs.remove(&last_position).ok_or(anyhow!("Couldn't remove last value"))?;
let new_position = last_position - 1;
*subs.entry(new_position).or_insert(0) += value;
fuel += value;
}
}
Ok(fuel)
}
fn part2<'a, I: Copy + IntoIterator<Item = &'a usize>>(input: I) -> Result<usize> {
#[derive(Debug)]
struct Occupancy {
cost: usize,
vessel_count: usize,
}
impl Occupancy {
fn new() -> Self {
let cost = 0;
let vessel_count = 0;
Self {
cost,
vessel_count,
}
}
fn add_vessel(&mut self) {
self.cost += 1;
self.vessel_count += 1;
}
fn merge(&mut self, other: Occupancy) -> Result<()> {
self.cost += other.cost + other.vessel_count;
self.vessel_count += other.vessel_count;
Ok(())
}
}
let mut subs: BTreeMap<usize, Occupancy> = BTreeMap::new();
let mut fuel = 0;
for position in input {
subs.entry(*position).or_insert_with(Occupancy::new).add_vessel();
}
while subs.len() > 1 {
let first_position = *subs.keys().next().ok_or(anyhow!("Couldn't get first position."))?;
let last_position = *subs.keys().rev().next()
.ok_or(anyhow!("Couldn't get last position."))?;
let first_costs = (*subs.get(&first_position).ok_or(anyhow!("Couldn't get first value."))?)
.cost;
let first_fuel = first_costs;
let last_costs = (*subs.get(&last_position).ok_or(anyhow!("Couldn't get last value."))?)
.cost;
let last_fuel = last_costs;
if first_fuel <= last_fuel {
let value = subs.remove(&first_position)
.ok_or(anyhow!("Couldn't remove first value"))?;
let new_position = first_position + 1;
let costs = subs.entry(new_position).or_insert_with(Occupancy::new);
costs.merge(value)?;
fuel += first_fuel;
}
if first_fuel >= last_fuel {
let value = subs.remove(&last_position).ok_or(anyhow!("Couldn't remove last value"))?;
let new_position = last_position - 1;
let costs = subs.entry(new_position).or_insert_with(Occupancy::new);
costs.merge(value)?;
fuel += last_fuel;
}
}
Ok(fuel)
}
fn main() -> Result<()> {
let ( do_part_1, do_part_2 ) = aoc::do_parts();
let filename = args().nth(1).ok_or(anyhow!("Missing input filename"))?;
let input = read_input(filename).context("Could not read input")?;
if do_part_1 {
let solution = part1(&input).context("No solution for part 1")?;
println!("Part1, solution found to be: {}", solution);
}
if do_part_2 {
let solution = part2(&input).context("No solution for part 2")?;
println!("Part2, solution found to be: {}", solution);
}
Ok(())
}
|
