LeetCode-66.Plus One

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本文介绍了一种针对数组表示的非负整数加一操作的优化算法。该算法通过从数组末尾开始检查每一位是否为9来决定如何进行加一操作，并在必要时扩展数组长度。文章提供了两种实现方案，后者是对前者的简化与优化。

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

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

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

public int[] PlusOne(int[] digits)
        {
            int n = digits.Length,i = 0;
            int[] res;
            while (i < n)
            {
                if (digits[i] != 9)
                    break;
                i++;
            }
            if (i==n)
            {
                res = new int[n + 1];
                res[0] = 1;
                return res;
            }
            res = digits;
            for (i = n-1; i >=0; i--)
            {
                if (digits[i] == 9)
                {
                    res[i] = 0;
                }
                else
                {
                    res[i] += 1;
                    return res;
                }
            }
            return res;
        }

优化一下

 public int[] PlusOne(int[] digits)
        {
            int n = digits.Length;
            int[] res = digits;
            for (int i = n - 1; i >= 0; i--)
            {
                if (digits[i] == 9)
                {
                    res[i] = 0;
                }
                else
                {
                    res[i] += 1;
                    return res;
                }
            }

            res = new int[n + 1];
            res[0] = 1;
            return res;
        }