public class Solution {

public int[] plusOne(int[] digits) {

if (digits == null)

return null;

if (digits.length == 0)

return new int[]{1};

int idxOfLastElem = digits.length - 1;

int carry = (digits[idxOfLastElem] + 1) / 10;

digits[idxOfLastElem] = (digits[idxOfLastElem] + 1) % 10;

for (int i = digits.length - 2; i >= 0 && carry != 0; i--) {

int sumOfBit = digits[i] + carry;

carry = sumOfBit / 10;

digits[i] = sumOfBit % 10;

}

if (carry == 0) {

return digits;

} else {

int[] result = new int[digits.length + 1];

result[0] = carry;

System.arraycopy(digits, 0, result, 1, digits.length);

return result;

}

}

}