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Java-based LeetCode algorithm problem solutions, regularly updated

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package g0001_0100.s0066_plus_one;

// #Easy #Top_Interview_Questions #Array #Math #Programming_Skills_II_Day_3 #Udemy_Arrays
// #2023_08_11_Time_0_ms_(100.00%)_Space_40.8_MB_(76.07%)

/**
 * 66 - Plus One\.
 *
 * Easy
 *
 * 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.
**/
public class Solution {
    public int[] plusOne(int[] digits) {
        int num = 1;
        int carry = 0;
        int sum;
        for (int i = digits.length - 1; i >= 0; i--) {
            if (i == digits.length - 1) {
                sum = digits[i] + carry + num;
            } else {
                sum = digits[i] + carry;
            }
            carry = sum / 10;
            digits[i] = sum % 10;
        }
        if (carry != 0) {
            int[] ans = new int[digits.length + 1];
            ans[0] = carry;
            System.arraycopy(digits, 0, ans, 1, ans.length - 1);
            return ans;
        }
        return digits;
    }
}