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

public class Solution { public int compareVersion(String version1, String version2) { } }

This problem is selected from LeetCode.

## Solution

Convert the two version strings to multiple parts and convert the parts to values and compare them.

Be careful to some special cases such as: 0.0 is same to 0.0.0.0.

The solution below assumes that the next level is 0 if there are no more levels in the shorter version number.

public class Solution { public int compareVersion(String version1, String version2) { String [] part1 = version1.split("\\."); String [] part2 = version2.split("\\."); int maxLength = Math.max(part1.length, part2.length); for(int i=0; i < maxLength; i++) { int v1 = i>=part1.length? 0: Integer.parseInt(part1[i]); int v2 = i>=part2.length? 0: Integer.parseInt(part2[i]); if(v1 > v2) return 1; if(v1 < v2) return -1; } return 0; } }

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