From 29cbde084bd87bfe8fea9ded4792edb0b4ac563d Mon Sep 17 00:00:00 2001
From: Andrei Ovcharenko <a@krot.name>
Date: Sat, 1 Aug 2026 04:52:29 +0300
Subject: [PATCH] Restore DigitalRoot legacy API compatibility

---
 src/main/java/kyu6/DigitalRoot.java     | 12 ++++++++++++
 src/test/java/kyu6/DigitalRootTest.java |  1 +
 2 files changed, 13 insertions(+)

diff --git a/src/main/java/kyu6/DigitalRoot.java b/src/main/java/kyu6/DigitalRoot.java
index f5af29e..fae3c4a 100644
--- a/src/main/java/kyu6/DigitalRoot.java
+++ b/src/main/java/kyu6/DigitalRoot.java
@@ -28,6 +28,18 @@ public static int digitalRoot(int n) {
         return result;
     }
 
+    /**
+     * Retains compatibility with the original Codewars API.
+     *
+     * @param n a non-negative integer
+     * @return the digital root of {@code n}
+     * @deprecated use {@link #digitalRoot(int)} instead
+     */
+    @Deprecated
+    public static int digital_root(int n) {
+        return digitalRoot(n);
+    }
+
     /**
      * Digital root is the recursive sum of all the digits in a number.
      * Given n, take the sum of the digits of n. If that value has more than one
diff --git a/src/test/java/kyu6/DigitalRootTest.java b/src/test/java/kyu6/DigitalRootTest.java
index 5d09716..f6a2668 100644
--- a/src/test/java/kyu6/DigitalRootTest.java
+++ b/src/test/java/kyu6/DigitalRootTest.java
@@ -21,5 +21,6 @@ class DigitalRootTest {
     void shouldReduceNumberToSingleDigit(int value, int expected) {
         assertEquals(expected, DigitalRoot.digitalRoot(value));
         assertEquals(expected, DigitalRoot.digitalRootRecursiveStream(value));
+        assertEquals(expected, DigitalRoot.digital_root(value));
     }
 }