add: d02, optimizations might come later

will namely add a numberic based algorithm, maybe even the stack
.to_string() is too slow

also might not do it, grialion already optimized tf out of it

2025/02/p2.rs

@@ -0,0 +1,54 @@
+#[unsafe(no_mangle)]
+fn challenge_usize(b: &[u8]) -> usize {
+    let mut total = 0;
+    let s = unsafe { str::from_utf8_unchecked(b) };
+
+    dbg!(is_repeating(b"11"));
+    let ranges = s.trim_end().split(',');
+    for range in ranges {
+        let (start, end) = range.split_once('-').unwrap();
+        if start.starts_with('0') || end.starts_with('0') {
+            continue;
+        }
+        let (start, end): (usize, usize) = (start.parse().unwrap(), end.parse().unwrap());
+        println!("{start}-{end}");
+
+        for id in start..=end {
+            let id_s = id.to_string();
+
+            if is_repeating(id_s.as_bytes()) {
+                total += id;
+                println!("-->> invalid {id_s}");
+            }
+        }
+    }
+
+    total
+}
+
+// fn is_repeating(s: &[u8]) -> bool {
+//     if !s.len().is_multiple_of(2) {
+//         return false;
+//     }
+
+//     let mid = s.len() / 2;
+//     let (left, right) = s.split_at(mid);
+//     left == right
+// }
+
+fn is_repeating(s: &[u8]) -> bool {
+    for sublen in 0..(s.len() / 2) {
+        let sublen = sublen + 1;
+        if !s.len().is_multiple_of(sublen) {
+            continue;
+        }
+        let pref = &s[0..sublen];
+
+        let is_repeating = s[sublen..].chunks_exact(sublen).all(|c| c == pref);
+        if is_repeating {
+            return true;
+        }
+    }
+
+    false
+}