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day3: problem 2 solution. this is ugly.

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This commit is contained in:
Keenan Tims 2023-12-05 18:49:36 -08:00
parent 1911614428
commit b1e7d7ad35
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3 changed files with 242 additions and 7 deletions
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85
3/Cargo.lock generated
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@ -2,6 +2,91 @@
# It is not intended for manual editing.
version = 3
[[package]]
name = "autocfg"
version = "1.1.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
[[package]]
name = "day3"
version = "0.1.0"
dependencies = [
"num",
]
[[package]]
name = "num"
version = "0.4.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "b05180d69e3da0e530ba2a1dae5110317e49e3b7f3d41be227dc5f92e49ee7af"
dependencies = [
"num-bigint",
"num-complex",
"num-integer",
"num-iter",
"num-rational",
"num-traits",
]
[[package]]
name = "num-bigint"
version = "0.4.4"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "608e7659b5c3d7cba262d894801b9ec9d00de989e8a82bd4bef91d08da45cdc0"
dependencies = [
"autocfg",
"num-integer",
"num-traits",
]
[[package]]
name = "num-complex"
version = "0.4.4"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "1ba157ca0885411de85d6ca030ba7e2a83a28636056c7c699b07c8b6f7383214"
dependencies = [
"num-traits",
]
[[package]]
name = "num-integer"
version = "0.1.45"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "225d3389fb3509a24c93f5c29eb6bde2586b98d9f016636dff58d7c6f7569cd9"
dependencies = [
"autocfg",
"num-traits",
]
[[package]]
name = "num-iter"
version = "0.1.43"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "7d03e6c028c5dc5cac6e2dec0efda81fc887605bb3d884578bb6d6bf7514e252"
dependencies = [
"autocfg",
"num-integer",
"num-traits",
]
[[package]]
name = "num-rational"
version = "0.4.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "0638a1c9d0a3c0914158145bc76cff373a75a627e6ecbfb71cbe6f453a5a19b0"
dependencies = [
"autocfg",
"num-bigint",
"num-integer",
"num-traits",
]
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version = "0.2.17"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "39e3200413f237f41ab11ad6d161bc7239c84dcb631773ccd7de3dfe4b5c267c"
dependencies = [
"autocfg",
]

1
3/Cargo.toml
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@ -6,3 +6,4 @@ edition = "2021"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
num = "0.4.1"

155
3/src/main.rs
View File

@ -1,5 +1,7 @@
use num::traits;
use std::fs::File;
use std::io::{BufRead, BufReader, Lines};
use std::ops::Range;
// --- Day 3: Gear Ratios ---
@ -52,6 +54,7 @@ fn main() {
// We will store the schematic as a 2D Vector of char
#[derive(Debug)]
struct Pos(usize, usize);
// Outer Vec holds rows, so addressing is column then row
@ -85,6 +88,19 @@ const ADJACENCY_OFFSETS: &[(i64, i64)] = &[
// We assume the schematic is composed of equal length lines
impl Schematic {
fn in_bounds<T: PartialOrd + num::traits::Zero + TryFrom<usize>>(&self, x: T, y: T) -> bool {
let x_bound: T = self.0[0]
.0
.len()
.try_into()
.unwrap_or_else(|_| panic!("bad bounds"));
let y_bound: T = self
.0
.len()
.try_into()
.unwrap_or_else(|_| panic!("bad bounds"));
x >= T::zero() && x < x_bound && y >= T::zero() && y < y_bound
}
fn at(&self, pos: &Pos) -> char {
self.0[pos.1].0[pos.0]
}
@ -94,6 +110,26 @@ impl Schematic {
let adj_x = (pos.0 as i64) + x_ofs;
let adj_y = (pos.1 as i64) + y_ofs;
if !self.in_bounds(adj_x, adj_y) {
false
} else {
let adj_c = self.at(&Pos(adj_x as usize, adj_y as usize));
adj_c != '.' && adj_c.is_ascii_punctuation()
}
})
}
fn is_gear(&self, pos: &Pos) -> bool {
if self.at(pos) != '*' {
return false;
}
ADJACENCY_OFFSETS
.iter()
.filter(|(x_ofs, y_ofs)| {
let adj_x = (pos.0 as i64) + x_ofs;
let adj_y = (pos.1 as i64) + y_ofs;
if adj_x < 0
|| adj_x >= self.0[pos.1].0.len() as i64
|| adj_y < 0
@ -102,9 +138,74 @@ impl Schematic {
false
} else {
let adj_c = self.at(&Pos(adj_x as usize, adj_y as usize));
adj_c != '.' && adj_c.is_ascii_punctuation()
adj_c.is_digit(10)
}
})
.count()
>= 2
}
fn gear_ratio(&self, pos: &Pos) -> Option<u64> {
if self.at(pos) != '*' {
return None;
}
let mut exclusions: Vec<(Range<usize>, i64)> = Vec::new();
let mut nums = (0u64, 0u64);
for (x_ofs, y_ofs) in ADJACENCY_OFFSETS {
let adj_x = (pos.0 as i64) + x_ofs;
let adj_y = (pos.1 as i64) + y_ofs;
if !self.in_bounds(adj_x, adj_y)
|| exclusions
.iter()
.any(|(ex_x_range, ex_y)| *ex_y == adj_y && ex_x_range.contains(&(adj_x as usize)))
{
continue;
}
let adj_c = self.at(&Pos(adj_x as usize, adj_y as usize));
if adj_c.is_digit(10) {
let mut num_start_x = adj_x as usize;
loop {
if num_start_x > 0
&& self
.at(&Pos((num_start_x - 1) as usize, adj_y as usize))
.is_digit(10)
{
num_start_x -= 1;
} else {
break;
}
}
let mut num_end_x = adj_x as usize;
loop {
if self.in_bounds(num_end_x + 1, adj_y as usize)
&& self
.at(&Pos((num_end_x + 1) as usize, adj_y as usize))
.is_digit(10)
{
num_end_x += 1;
} else {
break;
}
}
// we have the bounds for the number, extract a slice
let num_slice = &self.0[adj_y as usize].0[num_start_x..num_end_x + 1];
let mut num = 0u64;
for c in num_slice {
num = num * 10 + c.to_digit(10).unwrap() as u64;
}
if nums.0 == 0 {
nums.0 = num
} else {
nums.1 = num;
return Some(nums.0 * nums.1);
}
exclusions.push((num_start_x..num_end_x + 1, adj_y));
}
}
None
}
}
@ -156,6 +257,54 @@ fn problem1(input: InputIter) -> u64 {
// PROBLEM 2 solution
fn problem2(input: InputIter) -> u64 {
0
// --- Part Two ---
// The engineer finds the missing part and installs it in the engine! As the engine
// springs to life, you jump in the closest gondola, finally ready to ascend to the
// water source.
// You don't seem to be going very fast, though. Maybe something is still wrong?
// Fortunately, the gondola has a phone labeled "help", so you pick it up and the
// engineer answers.
// Before you can explain the situation, she suggests that you look out the window.
// There stands the engineer, holding a phone in one hand and waving with the other.
// You're going so slowly that you haven't even left the station. You exit the gondola.
// The missing part wasn't the only issue - one of the gears in the engine is wrong. A
// gear is any * symbol that is adjacent to exactly two part numbers. Its gear ratio is
// the result of multiplying those two numbers together.
// This time, you need to find the gear ratio of every gear and add them all up so that
// the engineer can figure out which gear needs to be replaced.
// Consider the same engine schematic again:
// 467..114.. ...*...... ..35..633. ......#... 617*...... .....+.58. ..592.....
// ......755. ...$.*.... .664.598..
// In this schematic, there are two gears. The first is in the top left; it has part
// numbers 467 and 35, so its gear ratio is 16345. The second gear is in the lower
// right; its gear ratio is 451490. (The * adjacent to 617 is not a gear because it is
// only adjacent to one part number.) Adding up all of the gear ratios produces 467835.
// What is the sum of all of the gear ratios in your engine schematic?
fn problem2_all_gear_ratios(schematic: &Schematic) -> Vec<u64> {
let mut gears = Vec::new();
for y in 0..schematic.0.len() {
for x in 0..schematic.0[0].0.len() {
match schematic.gear_ratio(&Pos(x, y)) {
Some(ratio) => gears.push(ratio),
_ => ()
}
}
}
gears
}
fn problem2(input: InputIter) -> u64 {
let schematic: Schematic = input.into();
problem2_all_gear_ratios(&schematic).iter().sum()
}