AddToArrayFormOfInteger.cpp

// Source : https://leetcode.com/problems/add-to-array-form-of-integer/
// Author : Hao Chen
// Date   : 2019-03-25

/***************************************************************************************************** 
 *
 * 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 <= A.length <= 10000
 * 	0 <= A[i] <= 9
 * 	0 <= K <= 10000
 * 	If A.length > 1, then A[0] != 0
 * 
 ******************************************************************************************************/

class Solution {
public:
    vector<int> addToArrayForm(vector<int>& A, int K) {
        int carry = K;
        for (int i = A.size() - 1; i >= 0 && carry > 0; i--) {
            int a = A[i] + carry;
            A[i] = a % 10 ;
            carry = a / 10;
        }

        while ( carry > 0 ) {
            A.insert(A.begin(), carry%10);
            carry /= 10;
        }

        return A;
    }
};