## 题目

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:

1 | Input: N = 3, K = 7 |

Example 2:

1 | Input: N = 2, K = 1 |

**Note:**

`1 <= N <= 9`

`0 <= K <= 9`

## 思路

DFS.

## 代码

1 | class Solution(object): |