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.

public class Solution {
    public int compareVersion(String version1, String version2) {
        int i = 0, j = 0;
        while (i < version1.length() || j < version2.length()) {
            int temp1 = 0, temp2 = 0;
            while (i < version1.length() && version1.charAt(i) != '.') {
                temp1 = temp1 * 10 + (version1.charAt(i++) - '0');
            }
            while (j < version2.length() && version2.charAt(j) != '.') {
                temp2 = temp2 * 10 + (version2.charAt(j++) - '0');
            }
            if (temp1 > temp2) {
                return 1;
            } else if (temp1 < temp2) {
                return -1;
            } else {
                i ++;
                j ++;
            }
        }
        return 0;
    }
}

class Solution(object):
    def compareVersion(self, version1, version2):
        """
        :type version1: str
        :type version2: str
        :rtype: int
        """

        if not version1 or not version2:
            return 0

        i = j = 0
        while i < len(version1) or j < len(version2):
            num1 = num2 = 0
            while i < len(version1) and version1[i] != '.':
                num1 = num1 * 10 + int(version1[i])
                i += 1
            while j < len(version2) and version2[j] != '.':
                num2 = num2 * 10 + int(version2[j])
                j += 1
            if num1 > num2:
                return 1
            elif num1 < num2:
                return -1
            else:
                i += 1
                j += 1
        return 0