2025 day2

aoc_utils/python_versions.txt

@@ -1,7 +1,9 @@
-3.7
 3.8
 3.9
 3.10
 3.11
 3.12
+3.13
+3.14
 pypy3.10
+pypy3.11

aoc_utils/src/lib.rs

@@ -3,6 +3,10 @@ use std::collections::{HashMap, HashSet};
 use std::fs::read_to_string;
 use std::ops::RemAssign;
 
+pub fn read_line(filename: &str) -> String {
+    read_to_string(filename).unwrap()
+}
+
 pub fn read_lines(filename: &str) -> Vec<String> {
     read_to_string(filename)
         .unwrap()

year_2025/input/day2.txt

@@ -0,0 +1 @@
+52500467-52574194,655624494-655688785,551225-576932,8418349387-8418411293,678-1464,33-79,74691-118637,8787869169-8787890635,9898977468-9899009083,548472423-548598890,337245835-337375280,482823-543075,926266-991539,1642682920-1642753675,3834997-3940764,1519-2653,39697698-39890329,3-21,3251796-3429874,3467-9298,26220798-26290827,80-124,200638-280634,666386-710754,21329-64315,250-528,9202893-9264498,819775-903385,292490-356024,22-32,2663033-2791382,133-239,56514707-56704320,432810-458773,4949427889-4949576808

year_2025/src/day2.rs

@@ -0,0 +1,104 @@
+pub fn execute() -> String {
+    let data = aoc_utils::read_line("input/day2.txt");
+
+    let part1 = get_all_invalids(&data, false).iter().sum::<usize>();
+    let part2 = get_all_invalids(&data, true).iter().sum::<usize>();
+
+    format!("{} {}", part1, part2)
+}
+type ProductID = usize;
+
+fn get_all_invalids(data: &String, any_splits: bool) -> Vec<ProductID> {
+    let ranges = parse_ranges(&data);
+    ranges
+        .iter()
+        .flat_map(|range| get_invalid_ids_in_range(range, any_splits))
+        .collect()
+}
+
+fn get_invalid_ids_in_range(range: &(ProductID, ProductID), any_splits: bool) -> Vec<ProductID> {
+    let mut invalids = vec![];
+
+    for n in range.0..range.1 + 1 {
+        if !is_valid_id(n, any_splits) {
+            invalids.push(n);
+        }
+    }
+
+    invalids
+}
+
+fn is_valid_id(n: ProductID, any_splits: bool) -> bool {
+    let digits = f32::log10(n as f32) as usize + 1;
+    assert!(digits > 0);
+
+    let max_splits = if any_splits { digits } else { 2 };
+
+    for splits in 2..max_splits + 1 {
+        if digits % splits == 0 {
+            if is_invalid_id(n, splits) {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+fn is_invalid_id(n: ProductID, splits: usize) -> bool {
+    let text = n.to_string().chars().collect::<Vec<char>>();
+    let digits = text.len();
+
+    for s in 1..splits {
+        for i in 0..digits / splits {
+            if text[i] != text[i + s * digits / splits] {
+                return false;
+            }
+        }
+    }
+    true
+}
+
+fn parse_ranges(data: &String) -> Vec<(ProductID, ProductID)> {
+    data.split(',')
+        .map(|range| {
+            let mut split = range.split('-');
+            (
+                split.next().unwrap().parse::<ProductID>().unwrap(),
+                split.next().unwrap().parse::<ProductID>().unwrap(),
+            )
+        })
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_example() {
+        let data = example();
+
+        let all_invalids = get_all_invalids(&data, false);
+        assert_eq!(all_invalids.iter().sum::<usize>(), 1227775554);
+
+        let all_invalids_really = get_all_invalids(&data, true);
+        assert_eq!(all_invalids_really.iter().sum::<usize>(), 4174379265);
+    }
+    #[test]
+    fn test_mine() {
+        assert_eq!(execute(), "41294979841 66500947346");
+    }
+
+    #[test]
+    fn test_parse_ranges() {
+        let ranges = parse_ranges(&example());
+        assert_eq!(ranges.len(), 11);
+        for range in ranges {
+            assert!(range.0 < range.1);
+        }
+    }
+
+    fn example() -> String {
+        "11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124".to_string()
+    }
+}

year_2025/src/main.rs

@@ -1,5 +1,7 @@
 mod day1;
+mod day2;
 
 fn main() {
     println!("Day  1: {}", day1::execute());
+    println!("Day  2: {}", day2::execute());
 }