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;
}
}