C++ 关联容器总结

map<string,int>::key_type;		//键的类型 const string
map<string,int>::mapped_type;	//值得类型 Int
map<string,int>::value_type;	//map所存元素的类型 pair<const string,int>类型

map<string ,int> m;
map<string,int> m(m2);
map<string,int> m(b,e);

map<string,int>::iterator ite = m.begin();
ite->first = "hwl";            //error:key is const

set<string> s;
set<string> s(s2);
set<string> s(b.e);

m["hwl"];				//m中没有键值为hwl的添加一个，采用值初始化方式初始化值。有的话访问m的值。
						//典型的用法：统计词频
string wrods;
map<string,int> words_count;
while (cin>>words)
{
	++words_count[words];
}

int occurs = 0;
if (words_count.count("hwl"))
{
	occurs = words_count["hwl"];
}

int occurs = 0;
map<string,int>::iterator ite = words_count.find("hwl");
if (ite != words_count.end())
{
	occurs = ite->second;
}

map<string,int>words;
set<string> keys;
//...1
pair<map<string,int>::iterator,bool> re = wrods.insert(map<string,int>::value_type("hwl",1));
pair<map<string,int>::iterator,bool> re = wrods.insert(make_pair("hwl",1));
pair<set<string>::iterator,bool> re = keys.insert("hwl");
//...2
wrods.insert(b,e);
keys.insert(b,e);
//...3
words.insert(ite,value_type);

map<string,int> words;		
words.erase("hwl");		//返回size_type类型（0 / 1）
words.erase(ite);		//返回void，ite所指的元素必须存在
words.erase(b,e);		//返回void

multimap<string,string> authors;
authors.insert(make_pair("hwl","IBNFGMGM"));
authors.insert(make_pair("hwl","IBN123333"));

multimap<string,string>::size_type cnt = authors.erase("hwl");//返回删除的个数
authors.erase(ite);//返回void
authors.erase(b,e);//返回void

authors.lower_bound(key);	//返回一个迭代器，指向键不小于key的第一个元素
authors.upper_bound(key);	//返回一个迭代器，指向键大于key的第一个元素
authors.equal_range(key);	//返回一个pair对象第一个元素等价于authors.lower_bound(key)，第二个等价于authors.upper_bound(key);
pair<authors::iterator,authors::iterator> pos = authors.equal_range(key);