PlusOne.java

package Lc66_PlusOne;

/**
 * 66. 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.
 *
 * 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 = [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 PlusOne {

    /**
     * Solution 1
     * Time complexity : O(n)
     * Space complexity : O(1)
     */
    public int[] plusOne(int[] digits) {
        int n = digits.length;
        for (int i = n - 1; i >= 0; i--) {
            if (digits[i] < 9) {
                digits[i]++;
                return digits;
            }
            digits[i] = 0;
        }
        int[] newArr = new int[n + 1];
        newArr[0] = 1;
        return newArr;
    }
}