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2025: Solution for Day 2, parts 1 & 2
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‎2024/day17/src/main.rs‎

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//! Advent of Code 2024: Day 17
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//! https://adventofcode.com/2024/day/17
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use std::{fs, io};
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use std::path::Path;
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fn main() {
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//let input = Input::from_file(format!("{}/input.txt", env!("CARGO_MANIFEST_DIR"))).expect("failed to read input");
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let input = Input::from_file(format!("{}/example2.txt", env!("CARGO_MANIFEST_DIR"))).expect("failed to read input");
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// Part 1
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println!("Part 1: {}", part1(&input));
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// Part 2
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let p2 = part2(&input);
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assert_eq!(State::new([p2, 0, 0]).run(&input.program), input.program);
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//println!("Part 2: {}", part2(&input));
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}
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#[derive(Copy, Clone, Debug, Eq, PartialEq)]
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enum Op {
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/// Division (output Register A)
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Adv,
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/// Bitwise XOR of Register B and literal
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Bxl,
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/// Combo
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Bst,
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/// Jump Non-Zero
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Jnz,
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/// Bitwise XOR of Register B and Register C
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Bxc,
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/// Output
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Out,
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/// Division (output Register B)
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Bdv,
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/// Division (output Register C)
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Cdv,
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}
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impl TryFrom<usize> for Op {
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type Error = usize;
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fn try_from(value: usize) -> Result<Self, Self::Error> {
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match value {
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0 => Ok(Self::Adv),
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1 => Ok(Self::Bxl),
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2 => Ok(Self::Bst),
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3 => Ok(Self::Jnz),
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4 => Ok(Self::Bxc),
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5 => Ok(Self::Out),
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6 => Ok(Self::Bdv),
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7 => Ok(Self::Cdv),
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opcode => Err(opcode)
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}
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}
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}
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const BITMASK: usize = 0b111;
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#[derive(Debug, Clone)]
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struct State {
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ip: usize,
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regs: [usize; 3],
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}
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impl State {
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fn new(regs: [usize; 3]) -> Self {
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State {
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ip: 0,
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regs,
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}
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}
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fn combo(&self, operand: usize) -> usize {
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match operand {
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0..=3 => operand,
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4 => self.regs[REG_A],
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5 => self.regs[REG_B],
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6 => self.regs[REG_C],
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_ => panic!("invalid combo operand: {operand}"),
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}
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}
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fn run(&mut self, program: &[usize]) -> Vec<usize> {
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let mut ip = 0;
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let mut output = vec![];
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while ip < program.len() {
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let op = Op::try_from(program[ip]).unwrap();
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let operand = program[ip + 1];
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ip += 2;
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match op {
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Op::Adv => {
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self.regs[REG_A] = self.regs[REG_A] >> self.combo(operand);
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}
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Op::Bxl => {
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self.regs[REG_B] = self.regs[REG_B] ^ operand;
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}
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Op::Bst => {
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self.regs[REG_B] = self.combo(operand) & BITMASK;
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}
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Op::Jnz => {
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if self.regs[REG_A] != 0 {
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ip = operand;
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}
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}
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Op::Bxc => {
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self.regs[REG_B] = self.regs[REG_B] ^ self.regs[REG_C];
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}
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Op::Out => {
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output.push(self.combo(operand) & BITMASK);
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}
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Op::Bdv => {
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self.regs[REG_B] = self.regs[REG_A] >> self.combo(operand);
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}
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Op::Cdv => {
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self.regs[REG_C] = self.regs[REG_A] >> self.combo(operand);
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}
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}
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}
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output
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}
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fn run2(&mut self, program: &[usize]) -> usize {
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let mut acc = 0;
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let mut z = 0;
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'outer: for x in program.iter().copied().rev() {
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println!("{x}: acc={acc}");
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for n in 0..=0b1111111111 {
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self.regs = [acc << 6 | n, 0, 0];
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let mut ip = 0;
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while ip < program.len() {
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let op = Op::try_from(program[ip]).unwrap();
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let operand = program[ip + 1];
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ip += 2;
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match op {
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Op::Adv => {
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self.regs[REG_A] = self.regs[REG_A] >> self.combo(operand);
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}
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Op::Bxl => {
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self.regs[REG_B] = self.regs[REG_B] ^ operand;
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}
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Op::Bst => {
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self.regs[REG_B] = self.combo(operand) & BITMASK;
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}
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Op::Jnz => {
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if self.regs[REG_A] != 0 {
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ip = operand;
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}
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}
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Op::Bxc => {
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self.regs[REG_B] = self.regs[REG_B] ^ self.regs[REG_C];
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}
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Op::Out => {
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if self.combo(operand) & BITMASK == x {
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acc = (acc << 3) | (n >> 3);
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z += 1;
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if z == program.len() {
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acc = (acc << 3) | (n & 0b111);
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}
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continue 'outer;
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}
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}
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Op::Bdv => {
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self.regs[REG_B] = self.regs[REG_A] >> self.combo(operand);
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}
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Op::Cdv => {
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self.regs[REG_C] = self.regs[REG_A] >> self.combo(operand);
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}
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}
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}
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}
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panic!();
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}
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println!("acc = {acc}");
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acc
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}
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fn combo2(&mut self, operand: usize, value: usize) {
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match operand {
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0 => assert_eq!(value, 0),
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1 => assert_eq!(value, 1),
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2 => assert_eq!(value, 2),
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3 => assert_eq!(value, 3),
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4 => self.regs[REG_A] = (self.regs[REG_A] & !0b111) | (value & 0b111),
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5 => self.regs[REG_B] = (self.regs[REG_B] & !0b111) | (value & 0b111),
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6 => self.regs[REG_C] = (self.regs[REG_C] & !0b111) | (value & 0b111),
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_ => panic!("unknown combo operand {operand}"),
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}
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}
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}
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fn part1(input: &Input) -> String {
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let output = State::new(input.registers).run(&input.program);
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let output: Vec<_> = output.into_iter().map(|x| x.to_string()).collect();
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output.join(",")
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}
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fn part2(input: &Input) -> usize {
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State::new(input.registers).run2(&input.program)
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}
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const REG_A: usize = 0;
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const REG_B: usize = 1;
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const REG_C: usize = 2;
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#[derive(Debug, Clone)]
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struct Input {
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registers: [usize; 3],
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program: Vec<usize>,
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}
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impl Input {
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fn from_file(path: impl AsRef<Path>) -> io::Result<Self> {
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let input = fs::read_to_string(path)?;
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let (chunk1, chunk2) = input.split_once("\n\n").unwrap();
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let mut registers = [0; 3];
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for (n, line) in chunk1.lines().enumerate() {
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let (_, value) = line.trim().split_once(": ").unwrap();
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registers[n] = value.parse().unwrap();
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}
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let (_, program) = chunk2.split_once(": ").unwrap();
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let program = program.trim().split(',').map(|s| s.parse().unwrap()).collect();
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Ok(Self { registers, program })
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn test_part1() {
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let input = Input::from_file("example1.txt").unwrap();
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assert_eq!(part1(&input), "4,6,3,5,6,3,5,2,1,0");
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}
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#[test]
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fn test_part1_solution() {
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let input = Input::from_file("input.txt").unwrap();
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assert_eq!(part1(&input), "5,1,3,4,3,7,2,1,7");
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}
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#[test]
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fn test_part2() {
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let input = Input::from_file("example2.txt").unwrap();
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assert_eq!(part2(&input), 117440);
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}
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#[test]
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fn test_part2_solution() {
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let input = Input::from_file("input.txt").unwrap();
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// Not 217269162253005
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assert_eq!(part2(&input), 0);
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}
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}

‎2024/day24/example1.txt‎

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‎2024/day24/example2.txt‎

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‎2025/Cargo.lock‎

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‎2025/Cargo.toml‎

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[workspace]
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members = [
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"day01",
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#"day02",
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"day02",
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#"day03",
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#"day04",
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#"day05",

‎2025/README.md‎

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## Solutions
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1. [Secret Entrance](day01) 🌟🌟
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2. [Gift Shop](day02) 🌟🌟

‎2025/day02/Cargo.toml‎

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[package]
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name = "day02"
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version = "0.1.0"
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edition = "2024"
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# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
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[dependencies]

‎2025/day02/example1.txt‎

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11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124

‎2025/day02/input.txt‎

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194-253,81430782-81451118,7709443-7841298,28377-38007,6841236050-6841305978,2222204551-2222236166,2623-4197,318169-385942,9827-16119,580816-616131,646982-683917,147-181,90-120,3545483464-3545590623,4304-5747,246071-314284,8484833630-8484865127,743942-795868,42-53,1435-2086,50480-60875,16232012-16441905,94275676-94433683,61509567-61686956,3872051-4002614,6918792899-6918944930,77312-106847,282-387,829099-1016957,288251787-288311732,6271381-6313272,9877430-10095488,59-87,161112-224439,851833788-851871307,6638265-6688423,434-624,1-20,26-40,6700-9791,990-1307,73673424-73819233

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