[LeetCode]36. Compare Version Numbers版本号比较

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

解法：将version string拆分为一个个整数，从前往后对比即可。

class Solution {
public:
    int compareVersion(string version1, string version2) {
        vector<string> vs1 = split(version1, '.');
        vector<string> vs2 = split(version2, '.');
        int s1 = vs1.size(), s2 = vs2.size();
        if (s1 == 0 && s2 == 0) return 0;
        else if (s1 == 0 || s2 == 0) return s2 == 0 ? 1 : -1;
        else
        {
            int i, j;
            for (i = 0, j = 0; i < s1 && j < s2; ++i, ++j)
            {
                if (stoi(vs1[i]) < stoi(vs2[j])) return -1;
                if (stoi(vs1[i]) > stoi(vs2[j])) return 1;
            }
            while (i < s1)
                if (stoi(vs1[i++]) > 0) return 1;
            while (j < s2)
                if (stoi(vs2[j++]) > 0) return -1;
            return 0;
        }
    }
private:
    vector<string> split(const string& str, const char delim)
    {
        vector<string> res;
        int start = 0, i = 0;
        for (int i = 0; i < str.size(); ++i)
        {
            if (str[i] == delim)
            {
                string s(str.begin() + start, str.begin() + i);
                if (!s.empty()) res.push_back(s);
                start = i + 1;
            }
        }
        string s(str.begin() + start, str.end());
        if (!s.empty()) res.push_back(s);
        return res;
    }
};