使map :: find操作大小写不敏感 [英] Making map::find operation case insensitive

问题描述

map :: find方法是否支持不区分大小写的搜索？

我有一个如下的地图

Does the map::find method support case insensitive search?
I have a map as follows

map<string,vector<string> > directory;  

，并希望以下搜索忽略大小写。

and want the below search to ignore case.

directory.find(search_string);

推荐答案

它没有默认。您将必须提供一个自定义比较器作为第三个参数。以下代码段将帮助您...

It does not by default. You will have to provide a custom comparator as a third argument. Following snippet will help you...

  /************************************************************************/
  /* Comparator for case-insensitive comparison in STL assos. containers  */
  /************************************************************************/
  struct ci_less : std::binary_function<std::string, std::string, bool>
  {
    // case-independent (ci) compare_less binary function
    struct nocase_compare : public std::binary_function<unsigned char,unsigned char,bool> 
    {
      bool operator() (const unsigned char& c1, const unsigned char& c2) const {
          return tolower (c1) < tolower (c2); 
      }
    };
    bool operator() (const std::string & s1, const std::string & s2) const {
      return std::lexicographical_compare 
        (s1.begin (), s1.end (),   // source range
        s2.begin (), s2.end (),   // dest range
        nocase_compare ());  // comparison
    }
  };

像 std :: map< std :: string，std :: vector< std :: string>，ci_less> myMap;

注意：std :: lexicographical_compare有一些细节细节。如果您考虑区域设置，字符串比较并不总是直接的。如果有兴趣，请参阅这个线程clc ++。

NOTE: std::lexicographical_compare has some nitty-gritty details. String comparison isn't always straightforward if you consider locales. See this thread on c.l.c++ if interested.

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