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85bbc6e9d8 ... 04dcd76a22

Author SHA1 Message Date
Tristan Daniël Maat 04dcd76a22
WIP: Re-implement using ndarray 2020-12-14 15:31:05 +00:00
Tristan Daniël Maat 279e9d8cc7
Re-implement day 11.1 with graphs 
This is to have a potentially nicer way to iterate neighbours, as well
as recursive directions.

While the former is neater than it was previously, the latter sadly
wasn't possible after all, and it's very inefficient.
 2020-12-12 23:49:27 +00:00
Tristan Daniël Maat 6dd5d1a04c
Complete day 11.1 2020-12-12 20:41:49 +00:00
4 changed files with 0 additions and 262 deletions
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78
day-13/Cargo.lock generated
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@ -1,78 +0,0 @@
# This file is automatically @generated by Cargo.
# It is not intended for manual editing.
[[package]]
name = "day-13"
version = "0.1.0"
dependencies = [
"indoc",
]
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name = "indoc"
version = "0.3.6"
source = "registry+https://github.com/rust-lang/crates.io-index"
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dependencies = [
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10
day-13/Cargo.toml
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@ -1,10 +0,0 @@
[package]
name = "day-13"
version = "0.1.0"
authors = ["Tristan Daniël Maat <tm@tlater.net>"]
edition = "2018"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
indoc = "0.3"

2
day-13/input
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@ -1,2 +0,0 @@
1000391
19,x,x,x,x,x,x,x,x,x,x,x,x,37,x,x,x,x,x,383,x,x,x,x,x,x,x,23,x,x,x,x,13,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,29,x,457,x,x,x,x,x,x,x,x,x,41,x,x,x,x,x,x,17

172
day-13/src/main.rs
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@ -1,172 +0,0 @@
use std::fs;
fn main() -> Result<(), Box<dyn std::error::Error>> {
let input = fs::read_to_string("input")?;
let (time, ids) = parse_notes(&input)?;
// Part 1
let (earliest, arrival) = find_closest_bus(time, &ids);
println!("{}", (arrival - time) * earliest);
// Part 2
let timestamp = find_gauss(&ids);
println!("{}", timestamp);
Ok(())
}
fn parse_notes(input: &str) -> Result<(u32, Vec<u32>), &str> {
let mut lines = input.lines();
let estimate = lines
.next()
.ok_or("Input too short")?
.parse()
.map_err(|_| "Estimate is not a number")?;
let ids = lines
.next()
.ok_or("Input too short")?
.split(',')
.map(|id| id.parse().unwrap_or(1))
.collect();
Ok((estimate, ids))
}
fn find_closest_bus(time: u32, ids: &Vec<u32>) -> (u32, u32) {
ids.iter()
.filter(|id| **id != 1)
.map(|id| {
let mut arrival = *id;
while arrival < time {
arrival += id
}
(*id, arrival)
})
.min_by_key(|id| id.1)
.expect("Must have at least one bus ID")
}
fn find_gauss(ids: &Vec<u32>) -> u128 {
let ids: Vec<u128> = ids.iter().map(|id| *id as u128).collect();
let product: u128 = ids.iter().product();
let gauss = |mut n: u128, mut d: u128, m: u128| -> u128 {
while d != 1 {
if m == 1 {
return 0;
};
let multiplier = if m > d {
m / d + (m % d != 0) as u128
} else {
1
};
n = (n * multiplier) % m;
d = (d * multiplier) % m;
}
n / d
};
(0..ids.len())
.map(|a| {
let b = product / ids[a];
let bi = gauss(1, b, ids[a]);
let a = (ids[a] * a as u128 - a as u128) % ids[a] as u128;
a * b * bi
})
.sum::<u128>()
% product
}
#[cfg(test)]
mod tests {
use super::*;
use indoc::indoc;
#[test]
fn test_simple() -> Result<(), Box<dyn std::error::Error>> {
let input = indoc!(
"939
7,13,x,x,59,x,31,19
"
);
let (time, ids) = parse_notes(input)?;
let (earliest, arrival) = find_closest_bus(time, &ids);
assert_eq!(arrival, 944);
Ok(())
}
#[test]
fn test_simple2() -> Result<(), Box<dyn std::error::Error>> {
let input = indoc!(
"939
17,x,13,19
"
);
let (time, ids) = parse_notes(input)?;
let timestamp = find_gauss(&ids);
assert_eq!(timestamp, 3417);
Ok(())
}
#[test]
fn test_simple3() -> Result<(), Box<dyn std::error::Error>> {
let input = indoc!(
"939
7,13,x,x,59,x,31,19
"
);
let (time, ids) = parse_notes(input)?;
let timestamp = find_gauss(&ids);
assert_eq!(timestamp, 1068781);
Ok(())
}
#[test]
fn test_simple4() -> Result<(), Box<dyn std::error::Error>> {
let input = indoc!(
"939
67,7,59,61
"
);
let (time, ids) = parse_notes(input)?;
let timestamp = find_gauss(&ids);
assert_eq!(timestamp, 754018);
Ok(())
}
#[test]
fn test_simple5() -> Result<(), Box<dyn std::error::Error>> {
let input = indoc!(
"939
67,x,7,59,61
"
);
let (time, ids) = parse_notes(input)?;
let timestamp = find_gauss(&ids);
assert_eq!(timestamp, 779210);
Ok(())
}
}