0066. Plus One

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

Description

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.

Example 1:

**Input:** digits = [1,2,3]
**Output:** [1,2,4]
**Explanation:** The array represents the integer 123.
Incrementing by one gives 123 + 1 = 124.
Thus, the result should be [1,2,4].

Example 2:

**Input:** digits = [4,3,2,1]
**Output:** [4,3,2,2]
**Explanation:** The array represents the integer 4321.
Incrementing by one gives 4321 + 1 = 4322.
Thus, the result should be [4,3,2,2].

Example 3:

**Input:** digits = [0]
**Output:** [1]
**Explanation:** The array represents the integer 0.
Incrementing by one gives 0 + 1 = 1.
Thus, the result should be [1].

Example 4:

**Input:** digits = [9]
**Output:** [1,0]
**Explanation:** The array represents the integer 9.
Incrementing by one gives 9 + 1 = 10.
Thus, the result should be [1,0].

Constraints:

• 1 <= digits.length <= 100

• 0 <= digits[i] <= 9

• digits does not contain any leading 0's.

ac

class Solution {
    public int[] plusOne(int[] digits) {
        // edge cases
        if (digits == null || digits.length == 0) return new int[0];

        // iterate
        int n  = digits.length;
        int carry =  (digits[n-1] + 1) / 10;
        digits[n-1] = (digits[n-1] + 1) % 10;

        for (int i = n - 2; i >= 0 && carry > 0; i--) {
            int tmp = carry;
            carry =  (tmp + digits[i]) / 10;
            digits[i] = (tmp + digits[i]) % 10;
        }

        // more digits than original
        int[] res = new int[n+1];
        if (carry > 0) {
            res[0] = carry;
            for (int i = 0; i < n; i++) {
                res[i+1] = digits[i];
            }
        } else {
            res = digits;
        }

        return res;
    }
}
/*
carry
*/