AddDigits : Accepted

README.md

@@ -143,6 +143,7 @@ My accepted leetcode solutions to some of the common interview problems.
 - [Count Primes](problems/src/math/CountPrimes.java) (Easy)
 - [Rotate Function](problems/src/math/RotateFunction.java) (Medium)
 - [Water and Jug Problem](problems/src/math/WaterAndJugProblem.java) (Medium)
+- [Add Digits](problems/src/math/AddDigits.java) (Easy)
 
 #### [Stack](problems/src/stack)
 

problems/src/math/AddDigits.java

@@ -0,0 +1,26 @@
+package math;
+
+/**
+ * Created by gouthamvidyapradhan on 02/08/2017.
+ * Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.
+
+ For example:
+
+ Given num = 38, the process is like: 3 + 8 = 11, 1 + 1 = 2. Since 2 has only one digit, return it.
+
+ Follow up:
+ Could you do it without any loop/recursion in O(1) runtime?
+
+ */
+public class AddDigits {
+
+    public static void main(String[] args) throws Exception{
+        System.out.println(new AddDigits().addDigits(38));
+    }
+
+    public int addDigits(int num) {
+        if(num == 0) return 0;
+        return num % 9 == 0 ? 9 : num % 9;
+    }
+
+}