CompareVersionNumbers165.java

public class CompareVersionNumbers165 {
    /*
     * Given two version numbers, version1 and version2, compare them.
     * 
     * Version numbers consist of one or more revisions joined by a dot '.'.
     *  Each revision consists of digits and may contain leading zeros. Every revision contains at least one character.
     *  Revisions are 0-indexed from left to right, with the leftmost revision being revision 0, the next revision being revision 1,
     *  and so on. For example 2.5.33 and 0.1 are valid version numbers.
     * 
     * To compare version numbers, compare their revisions in left-to-right order. 
     * Revisions are compared using their integer value ignoring any leading zeros.
     * This means that revisions 1 and 001 are considered equal. If a version number does not specify a revision at an index, 
     * then treat the revision as 0. For example, version 1.0 is less than version 1.1 because their revision 0s are the same,
     * but their revision 1s are 0 and 1 respectively, and 0 < 1.
     * 
     * Return the following:
     * 
     * If version1 < version2, return -1.
     * If version1 > version2, return 1.
     * Otherwise, return 0.
     * 
     */

     class Solution {
        public int compareVersion(String v1, String v2) {
            int n = v1.length() ;
            int m = v2.length() ;
            int i =0 , j =0 ;
            while (i < n || j < m) {
                int num1 = 0 ,num2 = 0;
                while (i < n && v1.charAt(i) != '.')
                    num1 = num1*10 + v1.charAt(i++) ;
                    
                while (j < m && v2.charAt(j) != '.')
                    num2 = num2*10 + v2.charAt(j++) ;
                
                if (num1 < num2) return -1; 
                else if (num2 < num1) return 1;
                i++;
                j++;
            }
            return 0 ;
        }
    }
 
}