Compare Version Numbers

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

把字符串以'.'分割，把分割後字符串轉化成整型，逐位比較即可。

class Solution {
public:
    int compareVersion(string version1, string version2) {
        int val1;
        int val2;
        int index1 = 0;
        int index2 = 0;
        while(index1<version1.length() || index2<version2.length()){
            val1 = 0;
            while(index1<version1.length()){
                if(version1[index1] == '.'){
                    index1++;
                    break;
                }else{
                    val1 = val1*10 + (version1[index1] - '0');
                    index1++;
                }
            }
            
            val2 = 0;
            while(index2<version2.length()){
                if(version2[index2] == '.'){
                    index2++;
                    break;
                }else{
                    val2 = val2*10 + (version2[index2] - '0');
                    index2++;
                }
            }
            
            if(val1 < val2){
                return -1;
            }
            if(val1 > val2){
                return 1;
            }
        }
        return 0;
    }
};