2025 day 2

Author: ictrobot

crates/year2025/src/day02.rs

@@ -0,0 +1,89 @@
+use utils::prelude::*;
+
+/// Finding numbers with repeated digit patterns within ranges.
+#[derive(Clone, Debug)]
+pub struct Day02 {
+    input: Vec<[u64; 2]>,
+}
+
+impl Day02 {
+    pub fn new(input: &str, _: InputType) -> Result<Self, InputError> {
+        Ok(Self {
+            input: parser::u64()
+                .repeat_n(b'-')
+                .repeat(b',', 1)
+                .parse_complete(input)?,
+        })
+    }
+
+    #[must_use]
+    pub fn part1(&self) -> u64 {
+        let mut total = 0;
+        for &[start, end] in &self.input {
+            'num_loop: for i in start..=end {
+                let num_digits = i.ilog10() + 1;
+
+                if num_digits % 2 != 0 {
+                    continue;
+                }
+
+                let pattern_digits = num_digits / 2;
+                let divisor = 10u64.pow(pattern_digits);
+                let pattern = i % divisor;
+
+                let mut remaining = i;
+                while remaining > 0 {
+                    let chunk = remaining % divisor;
+                    if chunk != pattern {
+                        continue 'num_loop;
+                    }
+                    remaining /= divisor;
+                }
+
+                total += i;
+            }
+        }
+        total
+    }
+
+    #[must_use]
+    pub fn part2(&self) -> u64 {
+        let mut total = 0;
+        for &[start, end] in &self.input {
+            for i in start..=end {
+                let num_digits = i.ilog10() + 1;
+
+                'pattern_loop: for pattern_digits in 1..=num_digits / 2 {
+                    if num_digits % pattern_digits != 0 {
+                        continue;
+                    }
+                    let divisor = 10u64.pow(pattern_digits);
+                    let pattern = i % divisor;
+
+                    let mut remaining = i;
+                    while remaining > 0 {
+                        let chunk = remaining % divisor;
+                        if chunk != pattern {
+                            continue 'pattern_loop;
+                        }
+                        remaining /= divisor;
+                    }
+
+                    total += i;
+                    break;
+                }
+            }
+        }
+        total
+    }
+}
+
+examples!(Day02 -> (u64, u64) [
+    {
+        input: "11-22,95-115,998-1012,1188511880-1188511890,222220-222224,\
+            1698522-1698528,446443-446449,38593856-38593862,565653-565659,\
+            824824821-824824827,2121212118-2121212124",
+        part1: 1227775554,
+        part2: 4174379265
+    },
+]);

crates/year2025/src/lib.rs

@@ -3,4 +3,5 @@
 
 utils::year!(2025 => year2025, ${
     1 => day01::Day01,
+    2 => day02::Day02,
 });