Given num = 38, the process is like: 3 + 8 = 11, 1 + 1 = 2. Since 2 has only one digit, return it{ public: int addDigits(int num) { return 1 + (num - 1) % 9; } };
num = 38
3 + 8 = 11
1 + 1 = 2
2
1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,……