Compare Version Numbers

Compare two version numbers version1 and version1.
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

注意一个特例： 1 和 1.0。

所以 在比较完对应的位数之后，还要查看多的位数是不是均为0.

还有就是在split(".") 时候，由于.是正则表达式中的符号，所以要转置。

public class Solution {
    public int compareVersion(String version1, String version2) {
        String[] parts1 = version1.split("\\.");
        String[] parts2 = version2.split("\\.");
        int len1 = parts1.length;
        int len2 = parts2.length;
        int i = 0;
        for(; i < len1 && i < len2; i ++){
            if(Integer.valueOf(parts1[i]) > Integer.valueOf(parts2[i])) return 1;
            if(Integer.valueOf(parts2[i]) > Integer.valueOf(parts1[i])) return -1;
        }
        if(len1 > len2){
            while(i < len1){
                if(Integer.valueOf(parts1[i++]) != 0) return 1;
            }
        }else if(len1 < len2){
            while(i < len2){
                if(Integer.valueOf(parts2[i++]) != 0) return -1;
            }
        }
        return 0;
    }
}