Lexicographical Numbers

MediumMathdfs

Solve this the way you would in the interview: out loud, on a timer, with an AI interviewer asking follow-ups while you code. You get a scored report at the end.

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Problem

Given an integer n, return all integers from 1 to n sorted in **lexicographical (dictionary) order** of their decimal representations. For example 10 comes before 2 because the string "10" sorts before "2". Aim for O(n) time and O(1) extra space beyond the output, which rules out converting everything to strings and sorting.

Examples

Input: n = 13
Output: [1,10,11,12,13,2,3,4,5,6,7,8,9]
Every number starting with the digit 1 comes before 2.
Input: n = 2
Output: [1,2]
Only two numbers.

Constraints

  • 1 <= n <= 5 * 10^4

What the interviewer grades

A correct solution is one of five scores. The report also grades problem understanding (did you clarify inputs and edge cases before coding), problem solving, communication while you work, code quality, and testing. See a sample report, or read up on the pattern in the lessons.

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