c++ - 按字符串长度对 CMap 键进行排序

Question

以前，我使用 STL 映射来执行上述任务。

struct ltstr
{
    bool operator()(std::string s1, std::string s2) const
    {
      const int l1 = s1.length();
      const int l2 = s2.length();
      if (l1 == l2) {
          // In alphabetical order.
          return s1.compare(s2) < 0;
      }
      // From longest length to shortest length.
      return l1 > l2;
    }
};
std::map<std::string, int, ltstr> m;

如何使用 CMap 执行相同的任务？

// How to make key sorted by string length?
CMap<CString, LPCTSTR, int, int> m;

Answer 1

你不能。来自 the MSDN documentation for CMap :

You might think that this iteration is sequential by key value; it is not. The sequence of retrieved elements is indeterminate.