Add an Integer to a Number Represented as Decimal Digits
Company: Google
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: easy
Interview Round: Other
### Problem
The array `num` stores a nonnegative integer's decimal digits from most significant to least significant. Return the decimal digit array for that integer plus k. The input number may be too long for a fixed-width integer.
```cpp
class Solution {
public:
vector<int> addToArrayForm(vector<int>& num, int k);
};
```
### Examples
**Example 1:**
```text
Input: num = [9,9], k = 5
Output: [1,0,4]
Explanation: 99+5=104, adding a new most-significant digit.
```
**Example 2:**
```text
Input: num = [0], k = 123
Output: [1,2,3]
Explanation: Zero plus123 has exactly those three digits.
```
### Constraints
- `1 <= num.length <= 10^4`.
- `0 <= num[i] <= 9`.
- There are no leading zeros except the number zero itself.
- `1 <= k <= 10^4`.
### Contract considerations
All array entries are individual decimal digits. k is positive under the source bounds.
```hint Read the boundary condition
Treat k as the initial carry rather than trying to convert the large digit array to one machine integer.
```
### Boundary reminders
All array entries are individual decimal digits. k is positive under the source bounds.
Overview: Add an Integer to a Number Represented as Decimal Digits. The array num stores a nonnegative integer's decimal digits from most significant to least significant.