165. 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

题目含义:版本号一般表示为 2.10，3.2.3这样的只含有数字和小数点的形式。比较两个版本号的大小。

 需要注意的是，2.1代表2号大版本的第1个小版本，2.10代表2号大版本的第10个小版本，所以2.10比2.1大。同时，2.1.0和2.1代表的是同一个版本。

    public int compareVersion(String version1, String version2) {
        String[] versionOne = version1.split("\.");
        String[] versionTwo = version2.split("\.");
        int length = Math.max(versionOne.length,versionTwo.length);
        for (int i=0;i<length;i++)
        {
            Integer value1 = i<versionOne.length?Integer.valueOf(versionOne[i]):0;
            Integer value2 = i<versionTwo.length?Integer.valueOf(versionTwo[i]):0;
            int result = value1.compareTo(value2);
            if (value1.compareTo(value2) != 0)
            {
                return result;
            }
        }
        return 0;       
    }