added digital root algorithm

Author: ankana2113

Diff for: Maths/DigitalRoot.js

@@ -0,0 +1,34 @@
+export const digitalRoot = (num: number): number => {
+  /**
+ * Calculates the digital root of a number in constant time.
+ * @param {number} num - The number to compute the digital root for.
+ * @returns {number} The digital root of the given number.
+ *
+ * @example
+ * digitalRoot(456) // returns 6
+ * digitalRoot(-999) // returns 9
+ * digitalRoot(0) // returns 0
+ */
+  if (num < 0) num = -num;
+  return num === 0 ? num : 1 + ((num - 1) % 9);
+};
+/*------------------------------------------------------------------------------------*/
+
+export const digitalRootRecursive = (num: number): number => {
+  /**
+ * Calculates the digital root of a number using recursion.
+ * @param {number} num - The number to compute the digital root for.
+ * @returns {number} The digital root of the given number.
+ *
+ * @example
+ * digitalRoot(456) // returns 6
+ * digitalRoot(999) // returns 9
+ * digitalRoot(0) // returns 0
+ */
+  if (num < 0) num = -num; // Handle negative input by converting to positive
+  if (num < 10) return num; // Base case for single-digit number
+
+  // Recursive case: sum digits and continue to reduce
+  const sum = (num % 10) + digitalRootRecursive(Math.floor(num / 10));
+  return digitalRootRecursive(sum); // Call digitalRoot recursively to reduce to single digit
+};