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

 

 ref:http://www.meetqun.com/thread-3384-1-1.html

public class Solution {
    // ref:http://www.meetqun.com/thread-3384-1-1.html
    public int compareVersion(String version1, String version2) {
        long v1=0, v2=0;
        int len1 = version1.length();
        int len2 = version2.length();
        int i=0, j=0;
        
        while(i<len1 || j< len2 ){
            v1 = 0;
            v2 = 0; // passed numbers left to '.', then only focus on digits right to '.'
            
            while(i<len1 && version1.charAt(i)!='.'){
                v1 = v1*10 + version1.charAt(i) - '0';   // here via minus '0', change char to number;
                i++;
            }
            i++;
            
            while(j< len2 && version2.charAt(j)!='.'){
                v2 = v2*10 + version2.charAt(j) - '0';
                j++;
            }
            j++;
            
            if(v1>v2) return 1;
            if(v1<v2) return -1;
            
        }
        
        return 0;
    }
}