165. 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

题意：比较版本号的大小。

思路：字符串的处理，stringstream的运用以及string成员函数find(), substr()的运用

class Solution {public:int compareVersion(string version1, string version2) {if (version1.find('.') == -1 && version2.find('.') == -1){return compare(version1, version2);}else{if (version1.find('.') == -1 && version2.find('.') != -1){int p = version2.find('.');string s = version2.substr(0, p);version2 = version2.substr(p + 1, version2.size());int r = compare(version1, s);if (r == 0){return compareVersion("0", version2);}else{return r;}}else if (version1.find('.') != -1 && version2.find('.') == -1){int p = version1.find('.');string s = version1.substr(0, p);version1 = version1.substr(p + 1, version1.size());int r= compare(s, version2);if (r == 0){return compareVersion(version1, "0");}else{return r;}}else{int p = version1.find('.');string s1 = version1.substr(0, p);version1 = version1.substr(p + 1, version1.size());int q = version2.find('.');string s2 = version2.substr(0, q);version2 = version2.substr(q + 1, version2.size());int r = compare(s1, s2);if (r == 0){return compareVersion(version1, version2);}else{return r;}}}}int compare(string s1, string s2){stringstream s;int a, b;s << s1;s >> a;s.clear();s << s2;s >> b;if (a > b)return 1;else if (a < b)return -1;elsereturn 0;}};