122 lines
3.0 KiB
Rust
122 lines
3.0 KiB
Rust
use std::collections::HashMap;
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fn main() -> Result<(), Box<dyn std::error::Error>> {
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// Part 1
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let numbers = parse_numbers("1,20,11,6,12,0")?;
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let result = play(&numbers, 2020);
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println!("{}", result);
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// Part 2
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let numbers = parse_numbers("1,20,11,6,12,0")?;
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let result = play(&numbers, 30000000);
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println!("{}", result);
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Ok(())
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}
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fn parse_numbers(input: &str) -> Result<Vec<u32>, std::num::ParseIntError> {
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input.split(',').map(|number| number.parse()).collect()
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}
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fn play(numbers: &Vec<u32>, turns: usize) -> u32 {
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let mut said = HashMap::new();
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for (turn, number) in numbers.iter().enumerate() {
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said.insert(*number, (turn + 1, 0));
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}
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let mut last = *numbers.last().expect("Must have at least one number");
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for turn in numbers.len()..turns {
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match said.get(&last) {
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Some((_, 0)) | None => {
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last = 0;
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let entry = said.entry(last).or_insert((0, 0));
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*entry = (turn + 1, entry.0);
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}
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Some((last_turn, last_last_turn)) => {
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last = (last_turn - last_last_turn) as u32;
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let entry = said.entry(last).or_insert((0, 0));
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*entry = (turn + 1, entry.0);
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}
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};
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}
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last
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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 test_simple() -> Result<(), Box<dyn std::error::Error>> {
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let input = "0,3,6";
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let numbers = parse_numbers(input)?;
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let result = play(&numbers, 2020);
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assert_eq!(result, 436);
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Ok(())
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}
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#[test]
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fn test_simple0() -> Result<(), Box<dyn std::error::Error>> {
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let input = "1,3,2";
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let numbers = parse_numbers(input)?;
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let result = play(&numbers, 2020);
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assert_eq!(result, 1);
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Ok(())
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}
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#[test]
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fn test_simple1() -> Result<(), Box<dyn std::error::Error>> {
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let input = "2,1,3";
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let numbers = parse_numbers(input)?;
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let result = play(&numbers, 2020);
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assert_eq!(result, 10);
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Ok(())
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}
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#[test]
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fn test_simple2() -> Result<(), Box<dyn std::error::Error>> {
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let input = "1,2,3";
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let numbers = parse_numbers(input)?;
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let result = play(&numbers, 2020);
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assert_eq!(result, 27);
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Ok(())
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}
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#[test]
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fn test_simple3() -> Result<(), Box<dyn std::error::Error>> {
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let input = "2,3,1";
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let numbers = parse_numbers(input)?;
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let result = play(&numbers, 2020);
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assert_eq!(result, 78);
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Ok(())
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}
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#[test]
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fn test_simple4() -> Result<(), Box<dyn std::error::Error>> {
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let input = "3,2,1";
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let numbers = parse_numbers(input)?;
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let result = play(&numbers, 2020);
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assert_eq!(result, 438);
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Ok(())
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}
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#[test]
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fn test_simple5() -> Result<(), Box<dyn std::error::Error>> {
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let input = "3,1,2";
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let numbers = parse_numbers(input)?;
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let result = play(&numbers, 2020);
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assert_eq!(result, 1836);
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Ok(())
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}
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}
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