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

Solution:
Split the two version string by dot and compare all element one by one in their integer form.

Some takeaways:
a. We need to escape dot when we use it as delimiter to split string => split.("\\.")
b. Corner case: 1.0.0.0 is equivalent to 1, so use larger length to do the iteration, and set integer value to 0 if i is larger than the length of current array.

  public int compareVersion(String version1, String version2) {  
     String[] versions1=version1.split("\\.");  
     String[] versions2=version2.split("\\.");  
     int i;  
     for(i=0;i<versions1.length || i<versions2.length;i++){  
       int a=i<versions1.length? Integer.parseInt(versions1[i]): 0;  
       int b=i<versions2.length? Integer.parseInt(versions2[i]):0;  
       if(a<b) return -1;  
       if(a>b) return 1;  
     }  
     return 0;  
   }