Add to Array-Form of Integer

Problem Statement - link #

The array-form of an integer num is an array representing its digits in left to right order.

• For example, for num = 1321, the array form is [1,3,2,1].

Given num, the array-form of an integer, and an integer k, return the array-form of the integer num + k.

Examples #

Example 1:

Input: num = [1,2,0,0], k = 34
Output: [1,2,3,4]
Explanation: 1200 + 34 = 1234

Example 2:

Input: num = [2,7,4], k = 181
Output: [4,5,5]
Explanation: 274 + 181 = 455

Example 3:

Input: num = [2,1,5], k = 806
Output: [1,0,2,1]
Explanation: 215 + 806 = 1021

Constraints #

• 1 <= num.length <= 10^4
• 0 <= num[i] <= 9
• num does not contain any leading zeros except for the zero itself.
• 1 <= k <= 10^4

Solutions #

class Solution {
public:
    vector<int> addToArrayForm(vector<int>& num, int k) {
        for(int i = num.size()-1; i >= 0; i--) {
            num[i] += k;
            k = num[i] / 10;
            num[i] %= 10;
        }
        while(k > 0) {
            num.insert(num.begin(), k % 10);
            k /= 10;
        }
        return num;        
    }
};