54 lines
1.2 KiB
Rust
54 lines
1.2 KiB
Rust
#![feature(test)]
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type Input = Vec<Equation>;
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#[derive(Debug)]
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struct Equation {
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result: i64,
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numbers: Vec<i64>,
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}
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fn setup(input: &str) -> Input {
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input
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.trim()
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.lines()
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.map(|line| {
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let mut nums = line.split_whitespace();
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let result = nums.next().unwrap().trim_end_matches(':').parse().unwrap();
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let numbers = nums.map(|n| n.parse().unwrap()).collect();
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Equation { result, numbers }
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})
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.collect()
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}
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fn solve<const P2: bool>(nums: &[i64], goal: i64) -> bool {
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if nums.len() == 1 {
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return nums[0] == goal;
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}
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let (&last, init) = nums.split_last().unwrap();
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let p = 10i64.pow(last.ilog10() + 1);
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(P2 && goal % p == last && solve::<P2>(init, goal / p))
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|| (goal % last == 0 && solve::<P2>(init, goal / last))
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|| solve::<P2>(init, goal - last)
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}
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fn part1(input: &Input) -> i64 {
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input
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.iter()
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.filter(|eq| solve::<false>(&eq.numbers, eq.result))
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.map(|eq| eq.result)
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.sum()
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}
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fn part2(input: &Input) -> i64 {
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input
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.iter()
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.filter(|eq| solve::<true>(&eq.numbers, eq.result))
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.map(|eq| eq.result)
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.sum()
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}
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aoc::main!(2024, 7, ex: 1);
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