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
139
140
141
142
143
144
145
146
147
148
|
use std::collections::{HashMap, HashSet};
static DAY: u8 = 3;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", part_sum(&input));
println!("{DAY}b: {}", gear_ratio_sum(&input));
}
#[derive(Eq, PartialEq, Clone, Copy, Hash)]
struct Position {
x: isize,
y: isize,
}
struct Schematics {
part_positions: HashMap<Position, char>,
}
impl Schematics {
fn new(input: &[String]) -> Schematics {
let mut part_positions = HashMap::new();
for (y, line) in input.iter().enumerate() {
for (x, c) in line.chars().enumerate() {
if c != '.' {
let pos = Position { x: x as isize, y: y as isize };
if !c.is_ascii_digit() {
part_positions.insert(pos, c);
}
}
}
}
Schematics { part_positions }
}
fn get_neighboring_parts(&self, pos: &Position) -> HashMap<Position, char> {
let mut parts = HashMap::new();
for y in -1 ..= 1 {
for x in -1 ..= 1 {
if let Some(part) = self.part_positions.get(&Position { x: pos.x + x, y: pos.y + y}) {
parts.insert(Position { x: pos.x + x, y: pos.y + y }, *part);
}
}
}
parts
}
fn has_neighboring_part(&self, pos: &Position) -> bool {
!self.get_neighboring_parts(pos).is_empty()
}
}
fn part_sum(input: &[String]) -> u32 {
let schematics = Schematics::new(input);
let mut part_numbers = Vec::new();
for (y, line) in input.iter().enumerate() {
let mut number = 0;
let mut is_part_number = false;
for (x, c) in line.chars().enumerate() {
if let Some(digit) = c.to_digit(10) {
number *= 10;
number += digit;
if schematics.has_neighboring_part(&Position { x: x as isize, y: y as isize }) {
is_part_number = true;
}
} else if number > 0 {
/* number ended within a line */
if is_part_number {
part_numbers.push(number);
}
number = 0;
is_part_number = false;
}
}
if number > 0 && is_part_number {
/* number ended at the end of line */
part_numbers.push(number);
}
}
part_numbers.iter()
.sum()
}
fn gear_ratio_sum(input: &[String]) -> u32 {
let schematics = Schematics::new(input);
let mut gear_neighbors = HashMap::<Position, Vec<u32>>::new();
for (y, line) in input.iter().enumerate() {
let mut number = 0;
let mut neighbors = HashSet::new();
for (x, c) in line.chars().enumerate() {
let pos = Position { x: x as isize, y: y as isize };
if let Some(digit) = c.to_digit(10) {
number *= 10;
number += digit;
for (pos, c) in schematics.get_neighboring_parts(&pos) {
if c == '*' {
neighbors.insert(pos);
}
}
} else if number > 0 {
/* number ended within a line */
for gear in &neighbors {
gear_neighbors.entry(*gear).or_default().push(number);
}
number = 0;
neighbors.clear();
}
}
if number > 0 {
/* number ended at the end of line */
for gear in &neighbors {
gear_neighbors.entry(*gear).or_default().push(number);
}
}
}
gear_neighbors.iter()
.filter(|(_, numbers)| numbers.len() == 2)
.map(|(_, numbers)| numbers.iter().product::<u32>())
.sum()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"467..114..",
"...*......",
"..35..633.",
"......#...",
"617*......",
".....+.58.",
"..592.....",
"......755.",
"...$.*....",
".664.598..",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(part_sum(&input), 4361);
assert_eq!(gear_ratio_sum(&input), 467835);
}
}
|
