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

public class Solution {
    public int compareVersion(String version1, String version2) {
        String[] levels1 = version1.split("\.");
        String[] levels2 = version2.split("\.");
    
        int length = Math.max(levels1.length, levels2.length);
        for (int i=0; i<length; i++) {
            Integer v1 = i < levels1.length ? Integer.parseInt(levels1[i]) : 0;
            Integer v2 = i < levels2.length ? Integer.parseInt(levels2[i]) : 0;
            int compare = v1.compareTo(v2);
            if (compare != 0) {
                return compare;
            }
        }
    
        return 0;
    }
}

split: http://stackoverflow.com/questions/7935858/the-split-method-in-java-does-not-work-on-a-dot

reference: https://leetcode.com/discuss/19118/accepted-small-java-solution