Implement 2025 - Day 2 - Part 2

2025/02.rs

@@ -17,18 +17,34 @@ fn main() {
     let mut result = 0;
     for r in ranges.iter() {
         for v in r.clone() {
-            let len = v.ilog10() + 1;
-            if len % 2 != 0 {
-                continue;
-            }
+            let v_len = v.ilog10() + 1;
+            
+            let mut iter = (1..=v_len/2).filter_map(|len| {
+                if v_len % len != 0 {
+                    return None;
+                }
 
-            let first_half = v / 10_usize.pow(len/2);
-            let second_half = v - (first_half * 10_usize.pow(len/2));
+                let mut seqs = (0..v_len/len).map(|i| {
+                    let offset = 10_usize.pow(i*len);
+                    let mask = 10_usize.pow(len);
 
-            if first_half == second_half {
+                    (v/offset) % mask
+                });
+
+                let first = match seqs.next() {
+                    Some(f) => f,
+                    None => return None,
+                };
+
+                let invalid = seqs.all(|s| s == first);
+                invalid.then_some((first, len, v_len/len))
+            });
+
+            let first = iter.next();
+            if first.is_some() {
+                println!("{} - {:?}", v, first);
                 result += v;
-                println!("Invalid {} - Halves ({}, {})", v, first_half, second_half);
-            }
+            }  
         }
     }