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Solution for day 13

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Inga 🏳‍🌈 2 years ago
parent
commit
3477c6fbcf
  1. 9
      day13-hard/Cargo.toml
  2. 64
      day13-hard/src/main.rs
  3. 9
      day13/Cargo.toml
  4. 23
      day13/src/main.rs

9
day13-hard/Cargo.toml

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[package]
name = "day13-hard"
version = "0.1.0"
authors = ["inga-lovinde <52715130+inga-lovinde@users.noreply.github.com>"]
edition = "2018"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]

64
day13-hard/src/main.rs

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use std::cmp::Reverse;
use std::io::{self, BufRead};
#[derive(Clone, Copy, Debug)]
struct Condition {
pub base: u128,
pub remainder: u128,
}
impl Condition {
fn new(base: u128, remainder: u128) -> Condition {
Condition {
base,
remainder,
}
}
}
impl Default for Condition {
fn default() -> Self {
Self {
base: 1,
remainder: 0,
}
}
}
// chinese remainder theorem, sieve method
// assuming all bases are coprime
fn solve(current: Condition, remaining_conditions: &[Condition]) -> Option<Condition> {
if remaining_conditions.len() == 0 {
return Some(current);
}
let first_condition = remaining_conditions[0];
for i in 0..first_condition.base {
if (i * current.base + current.remainder) % first_condition.base == first_condition.remainder {
return solve(Condition::new(current.base * first_condition.base, i * current.base + current.remainder), &remaining_conditions[1..]);
}
}
return None;
}
fn main() {
let stdin = io::stdin();
let mut stdin_lines = stdin.lock().lines();
let _timestamp: u128 = stdin_lines.next().unwrap().unwrap().parse().unwrap();
let mut conditions: Vec<_> = stdin_lines.next().unwrap().unwrap().split(",")
.enumerate()
.filter(|(_index, entry)| *entry != "x")
.map(|(index, entry)| (entry.parse::<u128>().unwrap(), index))
.map(|(base, index)| Condition::new(base, (-(index as i128)).rem_euclid(base as i128) as u128))
.collect();
conditions.sort_by_key(|condition| Reverse(condition.base));
for condition in conditions.iter() {
println!("{:?}", condition);
}
let solution = solve(Condition::default(), &conditions).unwrap();
println!("{:?}", solution);
}

9
day13/Cargo.toml

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[package]
name = "day13"
version = "0.1.0"
authors = ["inga-lovinde <52715130+inga-lovinde@users.noreply.github.com>"]
edition = "2018"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]

23
day13/src/main.rs

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use std::io::{self, BufRead};
fn get_wait_time(timestamp: u64, bus_number: u64) -> u64 {
let remainder = timestamp % bus_number;
if remainder == 0 {
return 0;
}
bus_number - remainder
}
fn main() {
let stdin = io::stdin();
let mut stdin_lines = stdin.lock().lines();
let timestamp: u64 = stdin_lines.next().unwrap().unwrap().parse().unwrap();
let earliest_bus_number = stdin_lines.next().unwrap().unwrap().split(",")
.filter(|&entry| entry != "x")
.map(|entry| entry.parse().unwrap())
.min_by_key(|&bus_number| get_wait_time(timestamp, bus_number))
.unwrap();
println!("{}", earliest_bus_number * get_wait_time(timestamp, earliest_bus_number));
}
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