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# 989. Add to Array-Form of Integer

For a non-negative integer `X`, the *array-form of `X`* is an array of its digits in left to right order.  For example, if `X = 1231`, then the array form is `[1,2,3,1]`.

Given the array-form `A` of a non-negative integer `X`, return the array-form of the integer `X+K`.

**Example 1:**

```
Input: A = [1,2,0,0], K = 34
Output: [1,2,3,4]
Explanation: 1200 + 34 = 1234
```

**Example 2:**

```
Input: A = [2,7,4], K = 181
Output: [4,5,5]
Explanation: 274 + 181 = 455
```

**Example 3:**

```
Input: A = [2,1,5], K = 806
Output: [1,0,2,1]
Explanation: 215 + 806 = 1021
```

**Example 4:**

```
Input: A = [9,9,9,9,9,9,9,9,9,9], K = 1
Output: [1,0,0,0,0,0,0,0,0,0,0]
Explanation: 9999999999 + 1 = 10000000000
```

**Note：**

1. `1 <= A.length <= 10000`
2. `0 <= A[i] <= 9`
3. `0 <= K <= 10000`
4. If `A.length > 1`, then `A[0] != 0`

```cpp
vector<int> addToArrayForm(vector<int>& A, int K) {
    int n = A.size(), carry = K;
    vector<int> res(A.begin(), A.end());
    for (int i = n - 1; i >= 0; --i) {
        int tmp = (i >= 0 ? A[i] : 0) + carry;
        res[i] = tmp % 10;
        carry = tmp / 10;
    }
    while (carry) {
        res.insert(res.begin(), carry % 10);
        carry /= 10;
    }
    return res;
}
```