advent of code 2025
adventofcode.com/2025
kokirigla.de
aoc
rust
1#![allow(dead_code)]
2use anyhow::Context;
3const INPUT: &str = include_str!("input/2/actual.txt");
4const IS_PART_2: bool = true;
5
6pub fn main() -> anyhow::Result<()> {
7 let ranges = parse(INPUT).context("parsing input")?;
8
9 let mut sum: u128 = 0;
10
11 for range in &ranges {
12 let range_sum = range
13 .sum_of_invalid_ids()
14 .context("summing invalid IDs for range")?;
15 sum += range_sum;
16 }
17
18 println!("TOTAL SUM OF INVALID NUMBERS IS {}", sum);
19
20 Ok(())
21}
22
23struct Range(u128, u128);
24
25impl Range {
26 pub fn sum_of_invalid_ids(&self) -> anyhow::Result<u128> {
27 let mut sum: u128 = 0;
28 for n in self.0..=self.1 {
29 if (if IS_PART_2 {
30 is_invalid_pt_2(n)
31 } else {
32 is_invalid(n)
33 })
34 .context("checking invalidity")?
35 {
36 // println!("{} is invalid", n);
37 sum += n
38 } else {
39 // println!("{} is valid", n);
40 }
41 }
42 Ok(sum)
43 }
44}
45
46fn parse(input: &str) -> anyhow::Result<Vec<Range>> {
47 let input = input.trim();
48 let mut ranges = Vec::new();
49 input
50 .split(',')
51 .try_for_each(|raw_range| -> anyhow::Result<()> {
52 let split_raw = raw_range.split('-').collect::<Vec<&str>>();
53 let first = split_raw
54 .get(0)
55 .context("getting first")?
56 .parse::<u128>()
57 .context("parsing first")?;
58 let second = split_raw
59 .get(1)
60 .context("getting second")?
61 .parse::<u128>()
62 .context("parsing second")?;
63 ranges.push(Range(first, second));
64 Ok(())
65 })
66 .context("running loop")?;
67 Ok(ranges)
68}
69
70fn is_invalid_pt_2(num: u128) -> anyhow::Result<bool> {
71 let as_string = num.to_string();
72 let length = as_string.len();
73
74 for i in 1..=length / 2 {
75 if length % i != 0 {
76 continue;
77 }
78
79 let pattern = &as_string[0..i];
80 let repetitions = length / i;
81
82 if pattern.repeat(repetitions) == as_string {
83 return Ok(true);
84 }
85 }
86
87 Ok(false)
88}
89
90fn is_invalid(num: u128) -> anyhow::Result<bool> {
91 let as_string = num.to_string();
92 let middle = as_string.len() / 2;
93
94 let split = as_string.split_at(middle);
95
96 let (left, right) = (split.0.to_string(), split.1.to_string());
97
98 Ok(left == right)
99}