<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>

class Solution {
public:
    int n;
    int k;
    void backtrack(vector<int>& ans, string& num) {
        if(num.length() == n) {
            int path = stoi(num);
            ans.push_back(path);
            return;
            
        }
        for(int i = 0; i < 10; i ++) {
            if(i == 0 && num.length() == 0) continue;
            if(num.empty()) {
                num.push_back(i +'0');
                backtrack(ans, num);
                num.pop_back();
            } else {
                int lastDigit = num.back() - '0';
                if(abs(lastDigit - i) == k){
                    num.push_back(i +'0');
                    backtrack(ans, num);
                    num.pop_back();
                }
            }
        }
        
    }
    vector<int> numsSameConsecDiff(int n, int k) {
        this->n = n;
        this->k = k;
        vector<int> ans;
        string num;
        backtrack(ans, num);
        return ans;
    }
};
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