Stepping Numbers

A stepping number is a number where each digit differs by exactly 1 from its neighbor(s). Given two integers n and m, return all stepping numbers in the range [n, m] in sorted order.

Examples
Input: [0,21]
Output: [0,1,2,3,4,5,6,7,8,9,10,12]
Hints

Stepping Numbers

A stepping number is a number where each digit differs by exactly 1 from its neighbor(s). Given two integers n and m, return all stepping numbers in the range [n, m] in sorted order.