Numbers With Same Consecutive Differences
<p>Given two integers n and k, return <em>an array of all the integers of length </em><code>n</code><em> where the difference between every two consecutive digits is </em><code>k</code>. You may return the answer in <strong>any order</strong>.</p>

<p>Note that the integers should not have leading zeros. Integers as <code>02</code> and <code>043</code> are not allowed.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> n = 3, k = 7
<strong>Output:</strong> [181,292,707,818,929]
<strong>Explanation:</strong> Note that 070 is not a valid number, because it has leading zeroes.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> n = 2, k = 1
<strong>Output:</strong> [10,12,21,23,32,34,43,45,54,56,65,67,76,78,87,89,98]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>2 &lt;= n &lt;= 9</code></li>
	<li><code>0 &lt;= k &lt;= 9</code></li>
</ul>
Breadth-First Search; Backtracking
func numsSameConsecDiff(n int, k int) (ans []int) {
	bounary := int(math.Pow10(n - 1))
	var dfs func(int)
	dfs = func(x int) {
		if x >= bounary {
			ans = append(ans, x)
			return
		}
		last := x % 10
		if last+k < 10 {
			dfs(x*10 + last + k)
		}
		if k > 0 && last-k >= 0 {
			dfs(x*10 + last - k)
		}
	}
	for i := 1; i < 10; i++ {
		dfs(i)
	}
	return
}
