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) {
        for(int index1 = 0, index2 = 0; index1 < version1.size() || index2<version2.size(); ++index1, ++index2){

            int num1 = 0;
            //直到遇到'.'就停止
            while(version1[index1] != '.' && index1 < version1.size())
                num1 = num1*10 + version1[index1++] - '0';

            int num2 = 0;    
            while(version2[index2] != '.' && index2 < version2.size())
                num2 = num2*10 + version2[index2++] - '0';

            if(num1 < num2) return -1;
            else if(num1 > num2) return 1;
        }
        return 0;
    }
};