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

September LeetCoding Challenge 21

Description

Lexicographical Numbers

Given an integer n, return all the numbers in the range [1, n] sorted in lexicographical order.

You must write an algorithm that runs in O(n) time and uses O(1) extra space. 

Example 1:

Input: n = 13
Output: [1,10,11,12,13,2,3,4,5,6,7,8,9]

Example 2:

Input: n = 2
Output: [1,2]

Constraints:

• 1 <= n <= 5 * 104

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  vector<int> lexicalOrder(int n) {
    int curInt = 1;
    vector<int> answer{1};
    while(answer.size() < n) {
      if(curInt * 10 <= n) {
        curInt *= 10;
        answer.push_back(curInt);
      } else {
        while(curInt % 10 == 9 || curInt == n) {
          int count = 1;
          curInt /= 10;
        }
        curInt += 1;
        answer.push_back(curInt);
      }
    }

    return answer;
  }
};