LeetCode – Add Digits (Java)
Given a nonnegative 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.
Java Solution 1  Recusion
public int addDigits(int num) { int sum=0; String s = String.valueOf(num); for(int i=0; i<s.length(); i++){ sum = sum + (s.charAt(i)'0'); } if(sum < 10){ return sum; }else{ return addDigits(sum); } } 
Java Solution 2  Math
public int addDigits(int num) { return num  9*((num1)/9); } 
<pre><code> String foo = "bar"; </code></pre>

Ahab Schmidt