Today I have done leetcode's September LeetCoding Challenge with cpp.

September LeetCoding Challenge 3

Description

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. For example, 01 has one leading zero and is invalid.

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]

Constraints:

• 2 <= n <= 9
• 0 <= k <= 9

Solution

class Solution {
  void solve(
    vector<int> &answer,
    int current,
    int k,
    int rest
  ) {
    if(!rest) {
      answer.push_back(current);
      return;
    }
    if(current % 10 >= k) {
      solve(answer, current * 10 + current % 10 - k, k, rest - 1);
    }
    if(k && current % 10 + k < 10) {
      solve(answer, current * 10 + current % 10 + k, k, rest - 1);
    }
  }
public:
  vector<int> numsSameConsecDiff(int n, int k) {
    vector<int> answer;
    for(int i = 1; i < 10; ++i) {
      solve(answer, i, k, n - 1);
    }
    return answer;
  }
};

// Accepted
// 81/81 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 49.91 % of cpp submissions (8.7 MB)