LeetCode62|数组形式的整数加法

示例 1：

输入：A = [1,2,0,0], K = 34
输出：[1,2,3,4]
解释：1200 + 34 = 1234
示例 2：

输入：A = [2,7,4], K = 181
输出：[4,5,5]
解释：274 + 181 = 455
示例 3：

输入：A = [2,1,5], K = 806
输出：[1,0,2,1]
解释：215 + 806 = 1021
示例 4：

输入：A = [9,9,9,9,9,9,9,9,9,9], K = 1
输出：[1,0,0,0,0,0,0,0,0,0,0]
解释：9999999999 + 1 = 10000000000
 

提示：

1 <= A.length <= 10000
0 <= A[i] <= 9
0 <= K <= 10000
如果 A.length > 1，那么 A[0] != 0

 
import java.util.ArrayList;
import java.util.List;

public class AddToArrayFormTest {
    public static void main(String[] args) {
        int[] A = {9, 9, 9, 9, 9, 9, 9, 9, 9, 9};
        int k = 1;
        List<Integer> list = addToArrayForm(A, k);
        System.out.println("list = " + list);
    }

    public static List<Integer> addToArrayForm(int[] A, int K) {
        StringBuilder s = new StringBuilder(A.length);
        for (int num : A) {
            s.append(num);
        }
        String s2 = String.valueOf(K);
        int size1 = s.length() - 1;
        int size2 = s2.length() - 1;
        StringBuilder stringBuilder = new StringBuilder();
        int carry = 0;
        while (size1 >= 0 || size2 >= 0 || carry > 0) {
            if (size1 >= 0) {
                carry += s.charAt(size1) - '0';
                size1 -= 1;
            }
            if (size2 >= 0) {
                carry += s2.charAt(size2) - '0';
                size2 -= 1;
            }
            stringBuilder.append(carry % 10);
            carry /= 10;
        }
        String string = stringBuilder.reverse().toString();
        char[] chars = string.toCharArray();
        List<Integer> list = new ArrayList<>();

        for (char aChar : chars) {
            list.add(aChar - '0');
        }
        return list;
    }
}