List Numbers Whose Neighboring Digits Differ by One
Company: eBay
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Other
### Problem
Return all integers in the inclusive interval [low,high] whose adjacent decimal digits differ in absolute value by exactly 1. Single-digit numbers, including 0, satisfy this rule. Return the list in increasing order, with no leading-zero representations.
```cpp
class Solution {
public:
vector<int> countSteppingNumbers(int low, int high);
};
```
### Examples
**Example 1:**
```text
Input: low = 20, high = 35
Output: [21,23,32,34]
Explanation: Each listed two-digit number has digit difference1; every other number in the range fails.
```
**Example 2:**
```text
Input: low = 0, high = 0
Output: [0]
Explanation: The sole candidate has no adjacent digit pair to violate the rule.
```
### Constraints
- `0 <= low <= high <= 2000000000`.
### Contract considerations
The rule concerns decimal adjacent digits, not differences between consecutive returned numbers.
```hint Read the boundary condition
Does the single-digit value zero meet the rule, and are both interval endpoints included?
```
### Boundary reminders
The rule concerns decimal adjacent digits, not differences between consecutive returned numbers.
Overview: List Numbers Whose Neighboring Digits Differ by One. Return all integers in the inclusive interval[low,high] whose adjacent decimal digits differ in absolute value by exactly1.