2019: day07: part 2
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27f6a072da
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@ -12,6 +12,7 @@ pub fn run() -> Result<String> {
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let mut res = String::with_capacity(128);
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writeln!(res, "part 1: {}", part1(INPUT)?)?;
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writeln!(res, "part 2: {}", part2(INPUT)?)?;
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Ok(res)
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}
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@ -67,6 +68,79 @@ fn part1(input: &str) -> Result<i64> {
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Ok(res)
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}
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fn part2(input: &str) -> Result<i64> {
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let memory = parse_memory(input)?;
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let combinations = permutations(&[5, 6, 7, 8, 9]);
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let mut res = 0;
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for combination in combinations {
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let intcodes = &mut [
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Intcode::with_memory(memory.clone()),
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Intcode::with_memory(memory.clone()),
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Intcode::with_memory(memory.clone()),
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Intcode::with_memory(memory.clone()),
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Intcode::with_memory(memory.clone()),
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];
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for (phase, intcode) in combination.iter().zip(intcodes.iter_mut()) {
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intcode.add_input(*phase);
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}
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intcodes[0].add_input(0);
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let mut signal = None;
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let mut num_halted = 0;
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loop {
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for i in 0..(intcodes.len() - 1) {
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let (first, second) = intcodes.split_at_mut(i + 1);
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let intcode = &mut first[i];
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let next = &mut second[0];
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let halted = intcode.run_and_wait()?;
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if halted {
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num_halted += 1;
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}
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for out in intcode.output.iter() {
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next.add_input(*out);
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}
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intcode.output.clear();
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}
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let last_index = intcodes.len() - 1;
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let (first, second) = intcodes.split_at_mut(last_index);
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let first = &mut first[0];
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let last = &mut second[0];
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let halted = last.run_and_wait()?;
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if halted {
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let out = last
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.output
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.last()
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.copied()
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.ok_or_else(|| err!("last amplifier halted without output"))?;
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signal = Some(out);
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} else {
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for out in last.output.iter() {
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first.add_input(*out);
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}
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last.output.clear();
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}
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if let Some(signal) = signal {
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res = std::cmp::max(res, signal);
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break;
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}
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if num_halted >= 4 {
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return Err(err!("all non final amplifiers halted, feedback loop stuck"));
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}
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}
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}
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Ok(res)
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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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@ -87,4 +161,19 @@ mod tests {
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fn part1_real() {
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assert_eq!(part1(INPUT).unwrap(), 844468);
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}
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const PROVIDED4: &str =
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"3,26,1001,26,-4,26,3,27,1002,27,2,27,1,27,26,27,4,27,1001,28,-1,28,1005,28,6,99,0,0,5";
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const PROVIDED5: &str = "3,52,1001,52,-5,52,3,53,1,52,56,54,1007,54,5,55,1005,55,26,1001,54,-5,54,1105,1,12,1,53,54,53,1008,54,0,55,1001,55,1,55,2,53,55,53,4,53,1001,56,-1,56,1005,56,6,99,0,0,0,0,10";
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#[test]
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fn part2_provided() {
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assert_eq!(part2(PROVIDED4).unwrap(), 139629729);
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assert_eq!(part2(PROVIDED5).unwrap(), 18216);
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}
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#[test]
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fn part2_real() {
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assert_eq!(part2(INPUT).unwrap(), 4215746);
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}
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}
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@ -24,12 +24,14 @@ enum Opcode {
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Halt,
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}
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#[derive(Debug)]
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pub struct Intcode {
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pub memory: Vec<i64>,
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input: Vec<i64>,
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pub output: Vec<i64>,
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ip: usize,
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next_input: usize,
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wait_input: bool,
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}
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impl Intcode {
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@ -46,6 +48,7 @@ impl Intcode {
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output: Vec::new(),
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ip: 0,
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next_input: 0,
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wait_input: false,
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}
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}
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@ -136,7 +139,7 @@ impl Intcode {
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}
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}
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pub fn run(&mut self) -> Result<()> {
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fn exec(&mut self) -> Result<bool> {
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loop {
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if self.ip >= self.memory.len() {
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return Err(err!("reached end of program without halting"));
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@ -165,10 +168,12 @@ impl Intcode {
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let input = if self.next_input < self.input.len() {
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let res = self.input[self.next_input];
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self.next_input += 1;
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Ok(res)
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res
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} else if self.wait_input {
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break Ok(false);
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} else {
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Err(err!("tried to read input but it was empty"))
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}?;
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break Err(err!("tried to read input but it was empty"));
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};
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dst.set(&mut self.memory, input)?;
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self.ip += 2;
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@ -223,11 +228,22 @@ impl Intcode {
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self.ip += 4;
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}
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Opcode::Halt => break Ok(()),
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Opcode::Halt => break Ok(true),
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}
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}
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}
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pub fn run_and_wait(&mut self) -> Result<bool> {
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self.wait_input = true;
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self.exec()
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}
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pub fn run(&mut self) -> Result<()> {
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self.wait_input = false;
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self.exec()?;
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Ok(())
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}
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pub fn get_day02_output(&self) -> Option<i64> {
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self.memory.get(0).copied()
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}
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