class Solution {public:    int compareVersion(string version1, string version2) {        if (version1 == version2) return 0;                int start1 = 0, cnt1 = 0, start2 = 0, cnt2 = 0;        string sub1, sub2;        while(1)        {            sub1.clear(); sub2.clear();            // 找version1中的子串，如到末尾了，那就赋“0”            cnt1 = 0;            while(start1 + cnt1 < version1.size() && version1[start1+cnt1] != ‘.‘)            {                cnt1++;            }            if (start1 < version1.size())                sub1 = version1.substr(start1, cnt1);                        cnt2 = 0;            while(start2 + cnt2 < version2.size() && version2[start2 + cnt2] != ‘.‘)            {                cnt2++;            }            if (start2 < version2.size())                sub2 = version2.substr(start2, cnt2);                            if (sub1.size() == 0) sub1 = "0";            if (sub2.size() == 0) sub2 = "0";                        // 不包括‘.‘,所以要加1            start1 = start1 + cnt1 + 1;            start2 = start2 + cnt2 + 1;                        if (stoi(sub2) > stoi(sub1)) return -1;            if (stoi(sub1) > stoi(sub2)) return 1;            // 子串相等并且都到了末尾才是相等，否则有的可能存在0.0.1            if (stoi(sub1) == stoi(sub2) && start1 >= version1.size() && start2 >= version2.size()) return 0;        }    }};