从零开始的LC刷题(15): Plus One

原题：

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

The digits are stored such that the most significant digit is at the head of the list, and each element in the array contain a single digit.

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

Example 1:

Input: [1,2,3]
Output: [1,2,4]
Explanation: The array represents the integer 123.

Example 2:

Input: [4,3,2,1]
Output: [4,3,2,2]
Explanation: The array represents the integer 4321.

就是往末尾加一然后注意进位，结果如下：

Success

Runtime: 4 ms, faster than 100.00% of C++ online submissions for Plus One.

Memory Usage: 8.6 MB, less than 53.99% of C++ online submissions for Plus One.

代码：

class Solution {
public:
    vector<int> plusOne(vector<int>& digits) {
        int i=digits.size()-1;
        while(i>=0&&digits[i]==9){
            digits[i]=0;
            i--;
        }
        if(i==-1){
            if(digits[0]!=0){digits[i]++;}
            else {digits.insert(digits.begin(),1);}
        }
        else {digits[i]++;}
        return digits;
    }
};