LeetCode 66. 加一

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.

解法：

class Solution {
    public int[] plusOne(int[] digits) {
        // Time: O(n)
        // Space: O(n)
        if (digits == null || digits.length < 1) {
            return digits;
        }
        int len = digits.length;
        for (int i = len - 1; i >= 0; --i) {
            if (digits[i] != 9) {
                digits[i]++;
                return digits;
            } else {
                digits[i] = 0;
            }
        }
        int[] resArr = new int[len + 1];
        resArr[0] = 1;
        return resArr;
    }
}