Compare Version Numbers

Problem

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 and Compare Solution

public class Solution {
    public int compareVersion(String version1, String version2) {
        String[] v1 = version1.split("\\.");
        String[] v2 = version2.split("\\.");
        int len = Math.max(v1.length, v2.length);
        for (int i = 0; i < len; i++) {
            int n1 = i < v1.length ? Integer.parseInt(v1[i]) : 0;
            int n2 = i < v2.length ? Integer.parseInt(v2[i]) : 0;
            if (n1 < n2) return -1;
            else if (n1 > n2) return 1;
        }
        return 0;
    }
}

Analysis

The tricky part of this problem is that two version can have different length
To avoid IndexOutofBorderException, we loop until the max of length and set 0 when it exceeds border
Then we return if there diff is not 0, otherwise, we keep looping