原题链接在这里：

题目：

Given a non-negative integer represented as a non-empty array of digits, plus one to the integer.

You may assume the integer do not contain any leading zero, except the number 0 itself.

The digits are stored such that the most significant digit is at the head of the list.

题解：

特殊情况是 全是9时需要新建一个数组。

Time Complexity: O(n). Space: O(n).

AC Java:

1 public class Solution { 2     public int[] plusOne(int[] digits) { 3         if(digits == null || digits.length == 0){ 4             return digits; 5         } 6         int carry = 1; 7         for(int i = digits.length-1; i>=0; i--){ 8             int cur = (digits[i]+carry)%10; 9             carry = (digits[i]+carry)/10;10             digits[i] = cur;11             12             if(carry == 0){13                 return digits;14             }15         }16         17         int [] res = new int[digits.length+1];18         res[0] = 1;19         return res;20     }21 }

跟上.