STL_MAP

水深无声 2022-07-17 04:16 235阅读 0赞

// accessing mapped values
    #include <iostream>
    #include <map>
    #include <string>
    
    int main()
    {
    	std::map<char, std::string> mymap;
    	//operator[] 返回指向second的指向的东西
    	mymap['a'] = "an element";
    	mymap['b'] = "another element";
    	mymap['c'] = mymap['b'];
    
    	std::cout << "mymap['a'] is " << mymap['a'] << '\n';
    	std::cout << "mymap['b'] is " << mymap['b'] << '\n';
    	std::cout << "mymap['c'] is " << mymap['c'] << '\n';
    	std::cout << "mymap['d'] is " << mymap['d'] << '\n';
    
    	std::cout << "mymap now contains " << mymap.size() << " elements.\n";
    	system("pause");
    	return 0;
    }

// map::insert (C++98)
    #include <iostream>
    #include <map>
    int main()
    {
    	std::map<char, int> mymap;
    	mymap.insert(std::pair<char, int>('a', 100));//pair使两个值关联起来
    	mymap.insert(std::pair<char, int>('z', 200));//pair键值对
    
    	std::pair<std::map<char, int>::iterator, bool> ret;
    	ret = mymap.insert(std::pair<char, int>('z', 500));
    	if (ret.second == false) {
    		std::cout << "element 'z' already existed";
    		std::cout << " with a value of " << ret.first->second << '\n';
    	}
    
    	// second insert function version (with hint position):
    	std::map<char, int>::iterator it = mymap.begin();
    	mymap.insert(it, std::pair<char, int>('b', 300));  // max efficiency inserting
    	mymap.insert(it, std::pair<char, int>('c', 400));  // no max efficiency inserting
    
    	// third insert function version (range insertion):
    	std::map<char, int> anothermap;
    	anothermap.insert(mymap.begin(), mymap.find('c'));
    
    	// showing contents:
    	std::cout << "mymap contains:\n";
    	for (it = mymap.begin(); it != mymap.end(); ++it)
    		std::cout << it->first << " => " << it->second << '\n';
    
    	std::cout << "anothermap contains:\n";
    	for (it = anothermap.begin(); it != anothermap.end(); ++it)
    		std::cout << it->first << " => " << it->second << '\n';
    	system("pause");
    	return 0;
    }

ERASE:

// erasing from map
    #include <iostream>
    #include <map>
    
    int main()
    {
    	std::map<char, int> mymap;
    	std::map<char, int>::iterator it;
    
    	// 插入数据
    	mymap['a'] = 10;
    	mymap['b'] = 20;
    	mymap['c'] = 30;
    	mymap['d'] = 40;
    	mymap['e'] = 50;
    	mymap['f'] = 60;
    
    	it = mymap.find('b');
    	mymap.erase(it);//找到b的迭代器删除
    
    	mymap.erase('c');//通过key值进行删除
    
    	it = mymap.find('e');
    	mymap.erase(it, mymap.end()); //删除e到结束的所有
    	//打印出所有的元素
    	for (it = mymap.begin(); it != mymap.end(); ++it)
    		std::cout << it->first << " => " << it->second << '\n';
    	system("pause");
    	return 0;
    }

// map::find
    #include <iostream>
    #include <map>
    
    int main()
    {
    	std::map<char, int> mymap;
    	std::map<char, int>::iterator it;
    
    	mymap['a'] = 50;
    	mymap['b'] = 100;
    	mymap['c'] = 150;
    	mymap['d'] = 200;
    
    	it = mymap.find('b');//找到b的迭代器
    	if (it != mymap.end())//找到后
    		mymap.erase(it);//删除
    	std::cout << "elements in mymap:" << '\n';
    	std::cout << "a => " << mymap.find('a')->second << '\n';
    	std::cout << "c => " << mymap.find('c')->second << '\n';
    	std::cout << "d => " << mymap.find('d')->second << '\n';
    	system("pause");
    	return 0;
    }

STL_MAP

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