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/all.rs

@@ -0,0 +1,66 @@
+#[unsafe(no_mangle)]
+fn challenge_usize_duple(b: &[u8]) -> (usize, usize) {
+    let mut total1 = 0;
+    let mut total2 = 0;
+    let s = unsafe { str::from_utf8_unchecked(b) };
+
+    let ranges = s.trim_end().split(',');
+    for range in ranges {
+        let (start, end) = range.split_once('-').unwrap();
+        let (start, end): (usize, usize) = (start.parse().unwrap(), end.parse().unwrap());
+
+        for id in start..=end {
+            let mut buf = [0; _];
+            let id_s = &fast_to_string(id, &mut buf);
+
+            if is_repeating1(id_s) {
+                total1 += id;
+            }
+            if is_repeating2(id_s) {
+                total2 += id;
+            }
+        }
+    }
+
+    (total1, total2)
+}
+
+const MAX_USIZE_LEN: usize = const { usize::MAX.ilog10() + 1 } as usize;
+/// Output is reversed btw
+fn fast_to_string(mut n: usize, into: &mut [u8; MAX_USIZE_LEN]) -> &mut [u8] {
+    let mut len = 0;
+    while n != 0 {
+        into[len] = (n % 10) as u8 + b'0';
+        n /= 10;
+        len += 1;
+    }
+
+    &mut into[0..len]
+}
+
+fn is_repeating1(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_repeating2(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
+}