40 lines
976 B
Rust
40 lines
976 B
Rust
const INPUT: &str = include_str!("../../data/day10");
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fn calc(input: &[u32], cache: &mut [Option<u64>], ndx: usize) -> u64 {
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if let Some(n) = cache[ndx] {
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n
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} else {
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let cur = input[ndx];
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let mut n = 0;
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for next in ndx+1..input.len() {
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if input[next] - cur > 3 { break; }
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n += calc(input, cache, next);
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}
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cache[ndx] = Some(n);
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n
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}
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}
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fn main() {
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let mut input: Vec<u32> = INPUT.lines().map(|s| s.parse().unwrap()).collect();
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input.sort();
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let mut prev = 0;
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let mut count = [0, 0, 0];
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{
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for &j in &input {
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count[(j - prev - 1) as usize] += 1;
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prev = j;
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}
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}
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count[2] += 1; // device always has diff of 3.
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println!("#(joltage diff 1) * #(joltage diff 3): {}", count[2] * count[0]);
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// insert outlet as first element
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input.insert(0, 0);
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let mut cache: Vec<Option<u64>> = input.iter().map(|_| None).collect();
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cache[input.len()-1] = Some(1); // always need last adapter
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println!("Combinations: {}", calc(&input, &mut cache, 0));
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}
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