Leetcode: Compare Version Numbers

题目：
Compare two version numbers version1 and version2.
If version1 > version2 return 1, if version1 < version2 return -1, otherwise return 0.

You may assume that the version strings are non-empty and contain only digits and the . character.
The . character does not represent a decimal point and is used to separate number sequences.
For instance, 2.5 is not “two and a half” or “half way to version three”, it is the fifth second-level revision of the second first-level revision.

Here is an example of version numbers ordering:
0.1 < 1.1 < 1.2 < 13.37

思路分析：
先将version字符串以点号分割放入vector中，然后将vector中的每个字符string类型转成int类型，然后依次进行int的比较。

C++示例代码：

class Solution 
{
private:
    /*
    将str以ch进行分割，结果保存在vector中返回
    */
    vector<string> split(string str, char ch)
    {
        vector<string> result;
        int index = 0;
        int count = 0;
        string substr;
        for (int i = 0; i < str.length(); i++)
        {
            if (str[i] == ch)
            {
                count = i - index;
                substr = str.substr(index, count);
                index = i + 1;
                result.push_back(substr);
            }
        }
        count = str.length()- index;
        substr = str.substr(index, count);
        result.push_back(substr);
        return result;
    }

    /*
    将vector中的string类型转换成int类型
    这里使用到了库函数stoi()
    */
    vector<int> toInt(vector<string> numbers)
    {
        int size = numbers.size();
        vector<int> intnums;
        intnums.reserve(size);
        for (int i = 0; i < size; i++)
        {
            intnums.push_back(stoi(numbers[i]));
        }
        return intnums;
    }

public:
    int compareVersion(string version1, string version2)
    {
        vector<string> strversion1 = split(version1, '.');
        vector<int> intversion1 = toInt(strversion1);

        vector<string> strversion2 = split(version2, '.');
        vector<int> intversion2 = toInt(strversion2);

        int size1 = intversion1.size();
        int size2 = intversion2.size();
        int size = size1;

        /*
        下面的ifelse是将两个vector的个数补齐，即使vector的  size是一样的，不足的补零。
        */
        if (size1 > size2)
        {
            size = size1;
            for (int i = size2; i < size; i++)
            {
                intversion2.push_back(0);
            }
        }
        else if (size1 < size2)
        {
            size = size2;
            for (int i = size1; i < size; i++)
            {
                intversion1.push_back(0);
            }
        }



        for (int i = 0; i < size; i++)
        {
            if (intversion1[i] > intversion2[i])
            {
                return 1;
            }
            else if (intversion1[i] < intversion2[i])
            {
                return -1;
            }
        }

        return 0;
    }
};