Numbers With Same Consecutive Differences

Return all non-negative integers of length N such that the absolute difference between every two consecutive digits is K.

Note that every number in the answer must not have leading zeros except for the number 0 itself. For example, 01 has one leading zero and is invalid, but 0 is valid.

You may return the answer in any order.

Example 1:

Input: N = 3, K = 7
Output: [181,292,707,818,929]
Explanation: Note that 070 is not a valid number, because it has leading zeroes.

Example 2:

Input: N = 2, K = 1
Output: [10,12,21,23,32,34,43,45,54,56,65,67,76,78,87,89,98]

Note:

1. 1 <= N <= 9

2. 0 <= K <= 9

class Solution {
    public int[] numsSameConsecDiff(int N, int K) {
        List<Integer> list = new ArrayList<>();
        if (N == 0)
            return new int[0];
        if (N == 1)
            list.add(0); // edge case
        dfs(N, K, list, 0);
        int[] ans = new int[list.size()];
        for (int i = 0; i < list.size(); i++)
            ans[i] = list.get(i);
        return ans;
    }

    public void dfs(int N, int K, List<Integer> list, int number) {
        // Base Case
        if (N == 0) {
            list.add(number);
            return;
        }
        for (int i = 0; i < 10; ++i) {
            // Do not add 0 at begining of a number
            if (i == 0 && number == 0)
                continue;
            // We add all the digits when we do not have any previous digit
            else if (number == 0 && i != 0)
                dfs(N - 1, K, list, i);
            else {
                // If the current digit, has a difference of K with last digit in number
                if (Math.abs((number % 10) - i) == K)
                    dfs(N - 1, K, list, number * 10 + i);
            }
        }
    }
}