Program to generate first n lexicographic numbers in python

Suppose we have a number n, we have to find first n numbers that are sorted in lexicographic sequence.

So, if the input is like n = 15, then the output will be [1, 10, 11, 12, 13, 14, 15, 2, 3, 4, 5, 6, 7, 8, 9]

To solve this, we will follow these steps:

• count := 1
• ans := a list with single element count
• while size of ans < n, do
  • count := count * 10
  • while count > n , do
    • count := quotient of count / 10
    • count := count + 1
    • while count mod 10 is same as 0, do
      • count := quotient of count / 10
    • insert count at the end of ans
• return ans

Let us see the following implementation to get better understanding:

Example Code

Live Demo

class Solution:
   def solve(self, n):
      count = 1
      ans = [count]

      while len(ans) < n:
         count *= 10
         while count > n:
            count = count // 10
            count += 1
            while count % 10 == 0:
               count = count // 10
               ans.append(count)
            return ans

ob = Solution()
n = 15
print(ob.solve(n))

Input

15

Output

[1, 10, 11, 12, 13, 14, 15, 2, 3, 4, 5, 6, 7, 8, 9]