From 9108278f6454435b07e5eb2bdb6cf516585d6e0a Mon Sep 17 00:00:00 2001
From: Jan Doumont <jan@6a616e.net>
Date: Fri, 12 Dec 2025 03:15:41 +0100
Subject: [PATCH] day2 :)

---
 src/day2.rs | 123 +++++++++++++++++-----------------------------------
 src/lib.rs  |   2 +-
 2 files changed, 41 insertions(+), 84 deletions(-)

diff --git a/src/day2.rs b/src/day2.rs
index e7ee62e..c4d85f2 100644
--- a/src/day2.rs
+++ b/src/day2.rs
@@ -1,9 +1,8 @@
+use std::collections::HashSet;
+
 #[aoc(day2, part1)]
 pub fn part1(input: &str) -> u64 {
     let ranges = parse(input);
-    for line in ranges.iter() {
-        println!("{:?}", line);
-    }
     let invalid_ids = invalid_ids(ranges);
     invalid_ids.iter().sum()
 }
@@ -11,11 +10,8 @@ pub fn part1(input: &str) -> u64 {
 #[aoc(day2, part2)]
 pub fn part2(input: &str) -> u64 {
     let ranges = parse(input);
-    for line in ranges.iter() {
-        println!("{:?}", line);
-    }
     let invalid_ids = invalid_ids_2(ranges);
-    invalid_ids.iter().sum()
+    invalid_ids
 }
 
 fn parse(input: &str) -> Vec<(&str, &str)> {
@@ -25,41 +21,50 @@ fn parse(input: &str) -> Vec<(&str, &str)> {
         .collect()
 }
 
-fn invalid_ids_2(ranges: Vec<(&str, &str)>) -> Vec<u64> {
-    let mut result = Vec::new();
+fn invalid_ids_2(ranges: Vec<(&str, &str)>) -> u64 {
+    let mut result: HashSet<u64> = HashSet::new();
 
-    for (start, end) in ranges {
-        for i in start.parse::<u64>().unwrap()..=end.parse::<u64>().unwrap() {
-            let i_str = i.to_string();
-            println!("{}", i_str);
-            let i_len = i_str.len();
-            for rl in 1..=i_len {
-                if i_len % rl != 0 {
-                    continue;
-                }
-                let mut condition = true;
-                for a in (0..i_len - rl).step_by(rl) {
-                    println!(
-                        "{:?} {:?} {:?} {} {}",
-                        i_str,
-                        &i_str[a..(a + rl)],
-                        &i_str[(a + rl)..(a + 2 * rl)],
-                        a,
-                        rl
-                    );
-                    if i_str[a..(a + rl)] != i_str[(a + rl)..(a + 2 * rl)] {
-                        condition = false;
-                        break;
+    for (from, to) in ranges {
+        let i_from = from.parse::<u64>().unwrap();
+        let i_to = to.parse::<u64>().unwrap();
+        for len in from.len()..=to.len() {
+            for n in (2..=len).filter(|n| len % n == 0) {
+                let l = len / n;
+                let min = match from.len() {
+                    x if x < len => 10u64.pow((len / n) as u32 - 1),
+                    _ => from[..l].parse::<u64>().unwrap(),
+                };
+                let max = match to.len() {
+                    x if x > len => 10u64.pow((len / n) as u32 + 1) - 1,
+                    _ => to[..l].parse::<u64>().unwrap(),
+                };
+                for num in min..=max {
+                    let candidate = num.to_string().repeat(n).parse::<u64>().unwrap();
+                    if candidate <= i_to && candidate >= i_from {
+                        result.insert(candidate);
                     }
                 }
-                if condition {
-                    result.push(i);
-                }
             }
         }
+        // if from.len() == to.len() {
+        //     println!("{} to {}", from, to,);
+        //     for n in (2..=(from.len() / 2).max(2)).filter(|n| from.len() % n == 0) {
+        //         //println!("{}", n);
+        //         let l = from.len() / n;
+        //         for num in from[..l].parse::<u64>().unwrap()..=to[..l].parse::<u64>().unwrap() {
+        //             let candidate = num.to_string().repeat(n).parse::<u64>().unwrap();
+        //             println!("{}", candidate);
+        //             if candidate <= i_to && candidate >= i_from {
+        //                 println!("selected!");
+        //                 result.insert(candidate);
+        //             }
+        //         }
+        //     }
+        // }
     }
-    result
+    result.iter().sum()
 }
+
 fn invalid_ids(ranges: Vec<(&str, &str)>) -> Vec<u64> {
     let mut result = Vec::new();
 
@@ -75,54 +80,6 @@ fn invalid_ids(ranges: Vec<(&str, &str)>) -> Vec<u64> {
             }
         }
     }
-    // for (start, end) in ranges {
-    //     let start_len = start.chars().count().to_owned();
-    //     let end_len = end.chars().count().to_owned();
-
-    //     let half_len = [start_len, end_len]
-    //         .into_iter()
-    //         .filter(|x| x % 2 == 0)
-    //         .max()
-    //         .unwrap_or(0)
-    //         / 2;
-
-    //     if half_len == 0 {
-    //         continue;
-    //     }
-
-    //     let start_num = String::from(
-    //         start
-    //             .chars()
-    //             .take(1.max(start_len - half_len))
-    //             .collect::<String>(),
-    //     )
-    //     .parse::<u64>()
-    //     .unwrap();
-    //     let end_num = String::from(end.chars().take(end_len - half_len).collect::<String>())
-    //         .parse::<u64>()
-    //         .unwrap();
-
-    //     let inner_start = String::from(start)[1.max(end_len / 2)..]
-    //         .parse::<u64>()
-    //         .unwrap_or(0);
-    //     let inner_end = String::from(end)[(end_len / 2)..].parse::<u64>().unwrap();
-
-    //     println!("{}-{}", start, end);
-    //     println!("{} {}", start_num, end_num);
-    //     println!("{} {}", inner_start, inner_end);
-
-    //     for num in start_num..=end_num {
-    //         if (inner_start..=inner_end).contains(&num) {
-    //             let id = num * 10_u64.pow(half_len as u32) + num;
-    //             if id.to_string().len() % 2 == 0 || id.to_string().len() == 1 {
-    //                 println!("{}", id);
-    //                 result.push(id)
-    //             }
-    //         }
-    //     }
-    //     // println!("{:?}", result);
-    // }
-    // // println!("{:?}", result);
     result
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index f1756ed..97a7339 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,7 +4,7 @@ extern crate aoc_runner;
 extern crate aoc_runner_derive;
 
 pub mod day1;
-// pub mod day2;
+pub mod day2;
 // pub mod day10;
 pub mod day11;
 pub mod day3;