728. Self Dividing Numbers

Leetcode Math

A self-dividing number is a number that is divisible by every digit it contains.

For example, 128 is a self-dividing number because 128 % 1 == 0, 128 % 2 == 0, and 128 % 8 == 0.

Also, a self-dividing number is not allowed to contain the digit zero.

Given a lower and upper number bound, output a list of every possible self dividing number, including the bounds if possible.

Example 1:

Input: 
left = 1, right = 22
Output: [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 15, 22]

Note: The boundaries of each input argument are 1 <= left <= right <= 10000.

分析

考察数字的基本操作。

public List<Integer> selfDividingNumbers(int left, int right) {
    List<Integer> res = new ArrayList<>();
    for (int num = left; num <= right; num++) {
        if (num < 10) {res.add(num); continue;}
        int numCopy = num;
        while (numCopy != 0) {
            int digit = numCopy % 10;
            if (digit == 0) break;
            if (num % digit != 0) break;
            numCopy /= 10;
        }
        if (numCopy == 0) res.add(num);
    }
    return res;
}