运用map并于执行期指定排序准则

该例展示以下技巧：

• 如何使用map
• 如何撰写和使用仿函数
• 如何在执行期定义排序规则
• 如何在“不在乎大小写”的情况下比较字符串

#include<iostream>

#include<map>

#include<algorithm>

#include<iomanip>

#include<string>

using namespace std;

class RuntimeStringCmp

{

public:

	enum cmp_mode{normal,nocase};

private:

	const cmp_mode mode;

	static bool nocase_compare(char c1, char c2)

	{

		return toupper(c1) < toupper(c2);

	}

public:

	RuntimeStringCmp(cmp_mode m = normal) :mode(m){}

	bool operator()(const string& s1, const string& s2)const

	{

		if (mode == normal)

			return s1 < s2;

		else

			return lexicographical_compare(s1.begin(), s1.end(), s2.begin(), s2.end(), nocase_compare);

	}

};

typedef map<string, string, RuntimeStringCmp> StringStringMap;

void fillAndPrint(StringStringMap& coll);

int main()

{

	StringStringMap coll1;

	fillAndPrint(coll1);

	RuntimeStringCmp ignorecase(RuntimeStringCmp::nocase);

	StringStringMap coll2(ignorecase);

	fillAndPrint(coll2);

	system("pause");

	return 0;

}

void fillAndPrint(StringStringMap& coll)

{

	coll["Deutschland"] = "Germany";

	coll["deutsch"] = "German";

	coll["Haken"] = "snag";

	coll["arbeiten"] = "work";

	coll["Hund"] = "dog";

	coll["gehen"] = "go";

	coll["Unternehmen"] = "enterprise";

	coll["unternehmen"] = "undertake";

	coll["gehen"] = "walk";

	coll["Bestatter"] = "undertaker";

	StringStringMap::iterator pos;

	cout.setf(ios::left, ios::adjustfield);

	for (pos = coll.begin(); pos != coll.end(); ++pos)

	{

		cout << setw(15) << pos->first.c_str() << " "

			<< pos->second << endl;

	}

	cout << endl;

}

本例摘自：C++标准库P212