stepping-numbers

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1215. Stepping Numbers (Medium)

A Stepping Number is an integer such that all of its adjacent digits have an absolute difference of exactly 1. For example, 321 is a Stepping Number while 421 is not.

Given two integers low and high, find and return a sorted list of all the Stepping Numbers in the range [low, high] inclusive.

 

Example 1:

Input: low = 0, high = 21
Output: [0,1,2,3,4,5,6,7,8,9,10,12,21]

 

Constraints:

• 0 <= low <= high <= 2 * 10^9

Related Topics

[Backtracking]

Hints

Hint 1

Try to generate the numbers using recursion.

Hint 2

In one step in the recursion, add a valid digit to the right of the current number.

Hint 3

Save the number if it's in the range between low and high.