diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/main.rs | 52 |
1 files changed, 51 insertions, 1 deletions
diff --git a/src/main.rs b/src/main.rs index f0f0336..0f0649e 100644 --- a/src/main.rs +++ b/src/main.rs @@ -1214,8 +1214,39 @@ fn day14() { println!("14b: {}", program.run_v2()); } +fn memory_number(numbers: &[usize], limit: usize) -> usize { + let mut memory = HashMap::new(); + let mut last_number = 0; + + for (i, number) in numbers.iter().enumerate() { + memory.insert(*number, (i, i, 0)); + last_number = *number; + } + + for i in memory.len()..limit { + let (pos0, pos1, count) = memory[&last_number]; + last_number = match count { + 0 => 0, + _ => pos1 - pos0, + }; + let update = match memory.get(&last_number) { + None => (i, i, 0), + Some((_, p1, c)) => (*p1, i, c + 1), + }; + memory.insert(last_number, update); + } + last_number +} + +fn day15() { + let input = [1, 2, 16, 19, 18, 0]; + + println!("15a: {}", memory_number(&input, 2020)); + println!("15b: {}", memory_number(&input, 30000000)); +} + fn main() { - day14(); + day15(); } #[cfg(test)] @@ -1492,4 +1523,23 @@ mod tests { let program = DockingProgram::new(&input); assert_eq!(program.run_v2(), 208); } + + #[test] + fn test_day15() { + assert_eq!(memory_number(&[1, 3, 2], 2020), 1); + assert_eq!(memory_number(&[2, 1, 3], 2020), 10); + assert_eq!(memory_number(&[1, 2, 3], 2020), 27); + assert_eq!(memory_number(&[2, 3, 1], 2020), 78); + assert_eq!(memory_number(&[3, 2, 1], 2020), 438); + assert_eq!(memory_number(&[3, 1, 2], 2020), 1836); + + // disabled due to long runtime + //assert_eq!(memory_number(&[0, 3, 6], 30000000), 175594); + //assert_eq!(memory_number(&[1, 3, 2], 30000000), 2578); + //assert_eq!(memory_number(&[2, 1, 3], 30000000), 3544142); + //assert_eq!(memory_number(&[1, 2, 3], 30000000), 261214); + //assert_eq!(memory_number(&[2, 3, 1], 30000000), 6895259); + //assert_eq!(memory_number(&[3, 2, 1], 30000000), 18); + //assert_eq!(memory_number(&[3, 1, 2], 30000000), 362); + } } |