Compare Version Numbers

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

class Solution {
public:
    int compareVersion(string version1, string version2) {
        vector<int> itgs1 = stois(version1);
		vector<int> itgs2 = stois(version2);
		size_t len = min(itgs1.size(), itgs2.size());
		for(int i = 0; i < len; i++)
		{
			if(itgs1[i] < itgs2[i])return -1;
			if(itgs1[i] > itgs2[i])return 1;
		}

		if(itgs1.size() > itgs2.size())return 1;
		else if(itgs1.size() == itgs2.size())return 0;
		else return -1;


    }

	vector<int> stois(string &s)
	{
		vector<int> itgs;
		int itg_start_idx = 0;
		for(int i = 0; i != s.size(); i++)
		{
			if(s[i] == '.')
			{
				//stirng 转为整数
				int val = stoi(s.substr(itg_start_idx, i));
				itgs.push_back(val);
				itg_start_idx = i+1;
			}
		}
		int val = stoi(s.substr(itg_start_idx, s.size()));
		if(val)itgs.push_back(val);
		//把最后的0 去掉
		for(int i = itgs.size() - 1; itgs.size() && !itgs[i]; i--)itgs.pop_back();
		return itgs;
	}
};