73 lines
1.6 KiB
Rust
73 lines
1.6 KiB
Rust
advent_of_code::solution!(9);
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type Seq = Vec<i32>;
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fn all_zero(s: &Seq) -> bool {
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s.iter().find(|t| **t != 0).is_none()
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}
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fn parse(input: &str) -> Vec<Seq> {
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input
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.lines()
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.filter_map(|line| {
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if !line.is_empty() {
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let nums = line.split(" ").map(|n| n.parse::<i32>().unwrap()).collect();
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Some(nums)
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} else {
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None
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}
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})
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.collect()
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}
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fn get_diffs(s: &Seq) -> Seq {
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let mut result: Seq = vec![];
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for index in 0..(s.len() - 1) {
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result.push(s[index + 1] - s[index]);
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}
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result
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}
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fn next_number(s: &Seq) -> i32 {
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if all_zero(s) {
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0
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} else {
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let d = get_diffs(s);
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s.last().unwrap() + next_number(&d)
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}
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}
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pub fn part_one(input: &str) -> Option<u32> {
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Some(parse(input).iter().map(|s| next_number(&s)).sum::<i32>().try_into().unwrap())
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}
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fn previous_number(s: &Seq) -> i32 {
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if all_zero(s) {
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0
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} else {
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let d = get_diffs(s);
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s[0] - previous_number(&d)
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}
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}
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pub fn part_two(input: &str) -> Option<u32> {
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Some(parse(input).iter().map(|s| previous_number(&s)).sum::<i32>().try_into().unwrap())
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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_part_one() {
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let result = part_one(&advent_of_code::template::read_file("examples", DAY));
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assert_eq!(result, Some(114));
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}
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#[test]
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fn test_part_two() {
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let result = part_two(&advent_of_code::template::read_file("examples", DAY));
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assert_eq!(result, Some(2));
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}
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}
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