1031. Add to Array-Form of Integer

• Difficulty: Easy

• Topics: Array

• Similar Questions:

  • Add Two Numbers

  • Plus One

  • Add Binary

  • Add Strings

Problem:

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

Solutions:

class Solution {
public:
    vector<int> addToArrayForm(vector<int>& A, int K) {
        vector<int> ret = A;
        reverse(ret.begin(), ret.end());

        int carry = K;
        int pos = 0;
        while (carry != 0) {
            if (pos == ret.size()) {
                ret.push_back(0);
            } 

            int val = carry + ret[pos];
            ret[pos] = val % 10;
            carry = val / 10;
            ++pos;
        }

        reverse(ret.begin(), ret.end());
        return ret;
    }
};