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;    }};