CompareVersionNumbers.java

/*

Source: https://leetcode.com/problems/compare-version-numbers/

Time: O(max(n, m)), where n and m are the length of the given strings i.e. version1 and version2 respectively.
Space: O(1), in-place

*/

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

    int len1 = version1.length();
    int len2 = version2.length();

    int i = 0;
    int j = 0;

    int num1 = 0;
    int num2 = 0;

    while(i < len1 || j < len2) {

      while(i < len1 && version1.charAt(i) != '.') {
        num1 = num1 * 10 + (version1.charAt(i) - '0');
        i++;
      }

      while(j < len2 && version2.charAt(j) != '.') {
        num2 = num2 * 10 + (version2.charAt(j) - '0');
        j++;
      }

      if(num1 > num2) {
        return 1;
      }

      if(num1 < num2) {
        return -1;
      }

      num1 = 0;
      num2 = 0;

      ++i;
      ++j;
    }

    return 0;
  }
}