[코테 풀이] Plus One

Q_66) Plus One

출처 : https://leetcode.com/problems/plus-one/

You are given a large integer represented as an integer array digits, where each digits[i] is the ith digit of the integer. The digits are ordered from most significant to least significant in left-to-right order. The large integer does not contain any leading 0's.

Increment the large integer by one and return the resulting array of digits.

class Solution {
    public int[] plusOne(int[] digits) {
        ArrayList<Integer> arrayList = new ArrayList<>();
        boolean carry = false;
        if (digits.length == 1) {
            if (digits[0] == 9) {
                return new int[]{1, 0};
            } else {
                return new int[]{digits[0] + 1};
            }
        } else {
            for (int d = digits.length - 1; d >= 0; d--) {
                if (d == digits.length - 1) {
//            올림 없을 때
                    if (digits[d] != 9) {
                        arrayList.add(0, digits[digits.length - 1] + 1);
                        for (int a = digits.length - 2; a >= 0; a--) {
                            arrayList.add(0, digits[a]);
                        }
                    }
//                올림 있을 때
                    else {
                        arrayList.add(0, 0);
                        carry = true;
                    }
                } else {
                    if (carry && digits[d] + 1 != 10) {
                        arrayList.add(0, digits[d] + 1);
                        carry = false;
                        for (int a = d - 1; a >= 0; a--) {
                            arrayList.add(0, digits[a]);
                        }
                    } else if (carry && digits[d] + 1 == 10) {
                        arrayList.add(0, 0);
                        carry = true;
                        if (d == 0) {
                            arrayList.add(0, 1);
                        }
                    }
                }
            }


        }
        int[] result = new int[arrayList.size()];
        for (int a = 0; a < arrayList.size(); a++) {
            result[a] = arrayList.get(a);
        }
        return result;
    }
}