From 782efd032d44d6be90189b7e734476e08a65591e Mon Sep 17 00:00:00 2001
From: Ruan Comelli <ruancomelli@gmail.com>
Date: Thu, 24 Aug 2023 18:58:32 -0300
Subject: [PATCH 1/2] ci: skip Rust checks in pre-commit hooks

---
 .pre-commit-config.yaml | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 37ec135..c5e4dee 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,7 +1,12 @@
 repos:
-- repo: https://github.com/doublify/pre-commit-rust
-  rev: v1.0
+# - repo: https://github.com/doublify/pre-commit-rust
+#   rev: v1.0
+#   hooks:
+#   - id: fmt
+#   - id: cargo-check
+#   - id: clippy
+- repo: https://github.com/pre-commit/pre-commit-hooks
+  rev: v4.4.0
   hooks:
-  - id: fmt
-  - id: cargo-check
-  - id: clippy
\ No newline at end of file
+  - id: end-of-file-fixer
+  - id: trailing-whitespace

From 2308a8fc1c54008569fbb63700cf608eb2474b3a Mon Sep 17 00:00:00 2001
From: Ruan Comelli <ruancomelli@gmail.com>
Date: Thu, 24 Aug 2023 18:58:41 -0300
Subject: [PATCH 2/2] refactor(exercise/armstrong-numbers): optimize
 implementation to use custom iterator type

---
 exercism/rust/armstrong-numbers/src/lib.rs | 42 ++++++++++++++++++----
 1 file changed, 36 insertions(+), 6 deletions(-)

diff --git a/exercism/rust/armstrong-numbers/src/lib.rs b/exercism/rust/armstrong-numbers/src/lib.rs
index 88cfc36..1134ddb 100644
--- a/exercism/rust/armstrong-numbers/src/lib.rs
+++ b/exercism/rust/armstrong-numbers/src/lib.rs
@@ -1,18 +1,48 @@
 pub fn is_armstrong_number(num: u32) -> bool {
-    let digits = digits(num);
-    let exponent = digits.len() as u32;
+    let digits = Digits::new(num);
+    let exponent = digits.num_digits;
 
     if exponent >= 10 {
+        // skip the calculation if the exponent is too large
         return false;
     }
 
-    num == digits.iter().map(|digit| digit.pow(exponent)).sum()
+    num == Digits::new(num).map(|digit| digit.pow(exponent)).sum()
 }
 
-fn digits(num: u32) -> Vec<u32> {
+struct Digits {
+    num: u32,
+    num_digits: u32,
+}
+
+impl Digits {
+    fn new(num: u32) -> Self {
+        Digits {
+            num,
+            num_digits: number_of_digits(num),
+        }
+    }
+}
+
+impl Iterator for Digits {
+    type Item = u32;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.num_digits == 0 {
+            None
+        } else {
+            let digit = self.num % 10;
+            self.num /= 10;
+            self.num_digits -= 1;
+            Some(digit)
+        }
+    }
+}
+
+fn number_of_digits(num: u32) -> u32 {
     if num < 10 {
-        vec![num]
+        1
     } else {
-        [vec![num % 10], digits(num / 10)].concat()
+        1 + number_of_digits(num / 10)
     }
 }