【LeetCode】165. Compare Version Numbers

题目：

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

提示：

这道题难就难在考虑的是否缜密，这里列举出一些典型的测试用例：

• ["01", "1"]
• ["10.6.5", "10.6"]
• ["1.0", "1"]

代码：

我自己的实现方法（比较臃肿，不推荐）：

class Solution {
public:
    int compareVersion(string version1, string version2) {
        int v1, v2, pos1, pos2;
        while (true) {
            if (version1.size() == 0) {
                if (version2.size() == 0) return 0;
                else version1 = "0";
            }
            else {
                if (version2.size() == 0) version2 = "0";
            }

            pos1 = version1.find(".");
            if (pos1 > -1) {
                v1 = atoi(version1.substr(0, pos1).c_str());
                version1 = version1.substr(pos1 + 1, version1.size() - 1);
            }
            else {
                v1 = atoi(version1.c_str());
                version1 = "";
            }
            pos2 = version2.find(".");
            if (pos2 > -1) {
                v2 = atoi(version2.substr(0, pos2).c_str());
                version2 = version2.substr(pos2 + 1, version2.size() - 1);
            }
            else {
                v2 = atoi(version2.c_str());
                version2 = "";
            }
            if (v1 > v2) return 1;
            if (v1 < v2) return -1;
        }

    }
};

论坛里某大神的方法（非常简洁，推荐）：

class Solution {
public:
    int compareVersion(string version1, string version2) {
        for (auto& w : version1) if (w == '.') w = ' ';
        for (auto& w : version2) if (w == '.') w = ' ';
        istringstream s1(version1), s2(version2);
        while (true) {
            int n1, n2;
            if (!(s1 >> n1)) n1 = 0;
            if (!(s2 >> n2)) n2 = 0;
            if (!s1 && !s2) return 0;
            if (n1 < n2) return -1;
            if (n1 > n2) return 1;
        }
    }
};