LC 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

Runtime:  136 ms, faster than 100.00% of C++ online submissions for Add to Array-Form of Integer.

Memory Usage:  11.9 MB, less than 100.00% of C++ online submissions for Add to Array-Form of Integer.

class Solution {
public:
  vector<int> addToArrayForm(vector<int>& A, int K) {
    vector<int> ka = itoarray(K);
    for(int a : ka) cout << a << endl;
    reverse(A.begin(), A.end());
    vector<int> ret;
    int endi = max(A.size(), ka.size());
    int add1, add2, sleft, sj; 
    sj = 0;
    for(int i=0; i<endi; i++) {
      add1 = add2 = sleft = 0;
      if(i < A.size()) add1 = A[i];
      if(i < ka.size()) add2 = ka[i];
      sleft = sj + add1 + add2;
      if(sleft >= 10) {sj = 1; sleft %= 10;}
      else sj = 0;
      ret.push_back(sleft);
    }   
    if(sj == 1) ret.push_back(1);
    reverse(ret.begin(), ret.end());
    return ret;
  }
  vector<int> itoarray(int K) {
    vector<int> a;
    while(K != 0) {
      a.push_back(K % 10);
      K /= 10; 
    }   
    return a;  
  }

};