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.

You may assume the default revision number for each level of a version number to be 0. For example, version number 3.4 has a revision number of 3 and 4 for its first and second level revision number. Its third and fourth level revision number are both 0.

Example 1:

Input: version1 = "0.1", version2 = "1.1"
Output: -1

Example 2:

Input: version1 = "1.0.1", version2 = "1"
Output: 1

Example 3:

Input: version1 = "7.5.2.4", version2 = "7.5.3"
Output: -1

Example 4:

Input: version1 = "1.01", version2 = "1.001"
Output: 0
Explanation: Ignoring leading zeroes, both “01” and “001" represent the same number “1”

Example 5:

Input: version1 = "1.0", version2 = "1.0.0"
Output: 0
Explanation: The first version number does not have a third level revision number, which means its third level revision number is default to "0"

Note:

• Version strings are composed of numeric strings separated by dots . and this numeric strings may have leading zeroes.
• Version strings do not start or end with dots, and they will not be two consecutive dots.

Solution: Split the String using "\.", 再对每个subversion进行比较

class Solution {
    public int compareVersion(String version1, String version2) {
        if (version1 == null || version1.length () == 0 || version2 == null || version2.length () == 0)
            return 0;
        
        String[] version1List = version1.split ("\\.");
        String[] version2List = version2.split ("\\.");
        
        // System.out.println (Arrays.toString (version1List));
        int len1 = version1List.length;
        int len2 = version2List.length;
        
        int len = Math.max (len1, len2);
        int i = 0;
        
        for (; i < len; i++) {
            int ver1 = i < len1 ? Integer.valueOf (version1List[i]) : 0;
            int ver2 = i < len2 ? Integer.valueOf (version2List[i]) : 0;
            
            // System.out.println (ver1 + " " + ver2);
            
            if (ver1 < ver2) {
                return -1;
            } else if (ver1 > ver2) {
                return 1;
            }
        }
        
        return 0;
    }
}