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CadiacCadiac
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Day 13 solutions
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‎aoc-solver/src/y2024/day13.rs

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,208 @@
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use itertools::Itertools;
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use crate::solution::{AocError, Solution};
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#[derive(Debug, PartialEq)]
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struct Machine {
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a: (i64, i64),
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b: (i64, i64),
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price: (i64, i64),
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}
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fn parse(input: &str) -> Result<Vec<Machine>, AocError> {
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let machines = input
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.trim()
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.split("\n\n")
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.map(|machine_input| {
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let (a_input, b_input, price_input) = machine_input
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.lines()
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.next_tuple()
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.ok_or_else(|| AocError::parse(machine_input, "Invalid machine"))?;
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let a = a_input
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.strip_prefix("Button A: X+")
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.and_then(|a| a.split_once(", Y+"))
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.and_then(|(x_str, y_str)| {
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let x = x_str.parse::<i64>().ok()?;
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let y = y_str.parse::<i64>().ok()?;
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Some((x, y))
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})
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.ok_or_else(|| AocError::parse(a_input, "Invalid button A"))?;
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let b = b_input
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.strip_prefix("Button B: X+")
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.and_then(|a| a.split_once(", Y+"))
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.and_then(|(x_str, y_str)| {
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let x = x_str.parse::<i64>().ok()?;
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let y = y_str.parse::<i64>().ok()?;
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Some((x, y))
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})
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.ok_or_else(|| AocError::parse(b_input, "Invalid button B"))?;
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let price = price_input
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.strip_prefix("Prize: X=")
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.and_then(|a| a.split_once(", Y="))
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.and_then(|(x_str, y_str)| {
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let x = x_str.parse::<i64>().ok()?;
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let y = y_str.parse::<i64>().ok()?;
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Some((x, y))
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})
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.ok_or_else(|| AocError::parse(b_input, "Invalid price"))?;
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Ok(Machine { a, b, price })
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})
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.try_collect()?;
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Ok(machines)
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}
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fn find_fewest_tokens(
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Machine { price, a, b }: &Machine,
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unit_conversion_error: bool,
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) -> Option<i64> {
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let price = if !unit_conversion_error {
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(price.0 + 10000000000000, price.1 + 10000000000000)
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} else {
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*price
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};
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// Solving `a_presses` and `b_presses`
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// from a system of two equations, accepting only integer solutions:
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// a_presses * a.x + b_presses * b.x = price.x
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// a_presses * a.y + b_presses * b.y = price.y
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let dividend_b = price.1 * a.0 - a.1 * price.0;
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let divisor_b = a.0 * b.1 - b.0 * a.1;
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let b_presses = dividend_b / divisor_b;
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let a_presses = (price.0 - b_presses * b.0) / a.0;
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let is_integer_a = (price.0 - b_presses * b.0) % a.0 == 0;
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let is_integer_b = dividend_b % divisor_b == 0;
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(is_integer_a && is_integer_b).then_some(3 * a_presses + b_presses)
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}
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pub struct Day13;
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impl Solution for Day13 {
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type A = i64;
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type B = i64;
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fn default_input(&self) -> &'static str {
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include_str!("../../../inputs/2024/day13.txt")
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}
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fn part_1(&self, input: &str) -> Result<i64, AocError> {
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let machines = parse(input)?;
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let fewest = machines
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.iter()
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.filter_map(|machine| find_fewest_tokens(machine, true))
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.sum();
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Ok(fewest)
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}
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fn part_2(&self, input: &str) -> Result<i64, AocError> {
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let machines = parse(input)?;
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let fewest = machines
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.iter()
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.filter_map(|machine| find_fewest_tokens(machine, false))
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.sum();
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Ok(fewest)
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn it_parses_input() {
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assert_eq!(
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parse(
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"Button A: X+94, Y+34\n\
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Button B: X+22, Y+67\n\
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Prize: X=8400, Y=5400\n\
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\n\
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Button A: X+26, Y+66\n\
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Button B: X+67, Y+21\n\
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Prize: X=12748, Y=12176"
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),
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Ok(vec![
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Machine {
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a: (94, 34),
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b: (22, 67),
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price: (8400, 5400)
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},
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Machine {
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a: (26, 66),
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b: (67, 21),
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price: (12748, 12176)
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}
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])
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)
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}
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#[test]
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fn it_solves_part1_example_1() {
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assert_eq!(
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Day13.part_1(
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"Button A: X+94, Y+34\n\
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Button B: X+22, Y+67\n\
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Prize: X=8400, Y=5400\n\
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\n\
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Button A: X+26, Y+66\n\
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Button B: X+67, Y+21\n\
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Prize: X=12748, Y=12176\n\
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\n\
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Button A: X+17, Y+86\n\
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Button B: X+84, Y+37\n\
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Prize: X=7870, Y=6450\n\
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\n\
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Button A: X+69, Y+23\n\
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Button B: X+27, Y+71\n\
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Prize: X=18641, Y=10279"
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),
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Ok(480)
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);
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}
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#[test]
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fn it_solves_part1_example_single() {
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assert_eq!(
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Day13.part_1(
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"Button A: X+94, Y+34\n\
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Button B: X+22, Y+67\n\
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Prize: X=8400, Y=5400"
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),
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Ok(280)
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);
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}
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#[test]
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fn it_solves_part2_example_1() {
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assert_eq!(
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Day13.part_2(
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"Button A: X+94, Y+34\n\
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Button B: X+22, Y+67\n\
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Prize: X=8400, Y=5400\n\
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\n\
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Button A: X+26, Y+66\n\
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Button B: X+67, Y+21\n\
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Prize: X=12748, Y=12176\n\
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\n\
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Button A: X+17, Y+86\n\
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Button B: X+84, Y+37\n\
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Prize: X=7870, Y=6450\n\
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\n\
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Button A: X+69, Y+23\n\
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Button B: X+27, Y+71\n\
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Prize: X=18641, Y=10279"
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),
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Ok(875318608908)
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);
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}
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}

‎aoc-solver/src/y2024/mod.rs

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Original file line numberDiff line numberDiff line change
@@ -12,7 +12,7 @@ pub mod day09;
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pub mod day10;
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pub mod day11;
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pub mod day12;
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// pub mod day13;
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pub mod day13;
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// pub mod day14;
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// pub mod day15;
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// pub mod day16;
@@ -26,7 +26,7 @@ pub mod day12;
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// pub mod day24;
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// pub mod day25;
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pub const MAX_DAYS: u8 = 12;
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pub const MAX_DAYS: u8 = 13;
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pub struct Y2024;
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@@ -45,7 +45,7 @@ impl Solver for Y2024 {
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10 => day10::Day10.run(input, 10, 2024),
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11 => day11::Day11.run(input, 11, 2024),
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12 => day12::Day12.run(input, 12, 2024),
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// 13 => day13::Day13.run(input, 13, 2024),
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13 => day13::Day13.run(input, 13, 2024),
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// 14 => day14::Day14.run(input, 14, 2024),
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// 15 => day15::Day15.run(input, 15, 2024),
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// 16 => day16::Day16.run(input, 16, 2024),
@@ -87,7 +87,7 @@ impl Solver for Y2024 {
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10 => include_str!("./day10.rs"),
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11 => include_str!("./day11.rs"),
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12 => include_str!("./day12.rs"),
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// 13 => include_str!("./day13.rs"),
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13 => include_str!("./day13.rs"),
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// 14 => include_str!("./day14.rs"),
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// 15 => include_str!("./day15.rs"),
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// 16 => include_str!("./day16.rs"),

‎aoc-web/src/header.rs

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@@ -31,6 +31,7 @@ pub fn header(props: &HeaderProps) -> Html {
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<NavLink route={Route::Solution { year: 2024, day: 10 }} current={props.route.clone()} text={"10"}/>
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<NavLink route={Route::Solution { year: 2024, day: 11 }} current={props.route.clone()} text={"11"}/>
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<NavLink route={Route::Solution { year: 2024, day: 12 }} current={props.route.clone()} text={"12"}/>
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<NavLink route={Route::Solution { year: 2024, day: 13 }} current={props.route.clone()} text={"13"}/>
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</>
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}
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},

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