165. Compare Version Numbers.cpp

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.

You may assume the default revision number for each level of a version number to be 0. For example, version number 3.4 has a revision number of 3 and 4 for its first and second level revision number. Its third and fourth level revision number are both 0.



Example 1:

Input: version1 = "0.1", version2 = "1.1"
Output: -1
Example 2:

Input: version1 = "1.0.1", version2 = "1"
Output: 1
Example 3:

Input: version1 = "7.5.2.4", version2 = "7.5.3"
Output: -1
Example 4:

Input: version1 = "1.01", version2 = "1.001"
Output: 0
Explanation: Ignoring leading zeroes, both “01” and “001" represent the same number “1”
Example 5:

Input: version1 = "1.0", version2 = "1.0.0"
Output: 0
Explanation: The first version number does not have a third level revision number, which means its third level revision number is default to "0"


Note:

Version strings are composed of numeric strings separated by dots . and this numeric strings may have leading zeroes.
Version strings do not start or end with dots, and they will not be two consecutive dots.








class Solution {
public:
    int compareVersion(string version1, string version2) {
        int n1=version1.length();
        int n2=version2.length();

        int num1=0, num2=0;
        int i=0, j=0;
        while(i<n1 || j<n2){
            while(i< n1 && version1[i]!='.'){
                num1=(num1*10)+(version1[i]-'0');
                i++;
            }
            while(j<n2 && version2[j]!='.'){
                num2=(num2*10)+(version2[j]-'0');
                j++;
            }

            if(num1>num2) return 1;
            if(num1<num2) return -1;

            num1=0;
            num2=0;

            i++;
            j++;
        }
        return 0;
    }
};