leetcode 各位相加

Given an integer num, repeatedly add all its digits until the result has only one digit, and return it.

func addDigits(num int) int {
    for ;num >= 10 ; {
        temp := 0
        for ; num != 0 ; {
            temp += num % 10
            num = (num - num % 10) / 10
        }
        num = temp
    }
    return num
}