Compare Version Numbers

Compare two version numbers version1 and version1.
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

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

 

简单，但不好写，需要细心

特例：1.0 1  1.0.0.0 1.0

1. int compareVersion(string version1, string version2) {
2. int vlen1 = version1.size();
3. int vlen2 = version2.size();
4. if(vlen1==0 && vlen2==0) return 0;
5. stringstream s1(version1);
6. stringstream s2(version2);
7. vector<int> value1;
8. vector<int> value2;
9. string tmpvalue;
10. while(getline(s1,tmpvalue,'.')) {
11. value1.push_back(atoi(tmpvalue.c_str()));
12. }
13. while(getline(s2,tmpvalue,'.')) {
14. value2.push_back(atoi(tmpvalue.c_str()));
15. }
16. int val_len1 = value1.size();
17. int val_len2 = value2.size();
18. int i = 0;
19. int j = 0;
20. while(i<val_len1 || j < val_len2) {
21. int real_1 = 0;
22. int real_2 = 0;
23. if(i<val_len1) real_1 = value1[i];
24. if(j<val_len2) real_2 = value2[j];
25. if(real_1 > real_2) return 1;
26. else if(real_1 < real_2) return -1;
27. i++;
28. j++;
29. }
30. return 0;
31. }

   学习：

size_t find (const string& str, size_t pos = 0) const;

size_t 为unsigned int， 如果找不到，则返回string::npos（无符号整数最大值）

string substr (size_t pos = 0, size_t len = npos) const;

pos 最大为len,如果大于，则返回out_of_range，所以要控制