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

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

分析：1.注意 “.” 要转译“\.”

         2. 主要consider many case 最简方法就是，没有就补0

public class Solution {
    public int compareVersion(String version1, String version2) {
        if(version1.equals(version2)) return 0;
        String[] v1 = version1.split("\.");
        String[] v2 = version2.split("\.");
        for(int i = 0 ; i < v1.length || i < v2.length ; i++){
            String index1 = (i >= v1.length ? "0" : v1[i]);
            String index2 = (i >= v2.length ? "0" : v2[i]);
            if(convertStrtoInt(index1) > convertStrtoInt(index2))
                return 1;
            else if (convertStrtoInt(index1) < convertStrtoInt(index2))
                return -1;
        }
        return 0;
    }
    public int convertStrtoInt(String s){
        int num = 0;
        for(int i = 0 ; i < s.length() ; i++){
            num = num * 10 + s.charAt(i) - '0';
        }
        return num;
    }
}