【C++】-- STL之unordered_map/unordered_set详解（三）

iterator find ( const key_type& k );

cout << um1.find("洒水车")->second << endl;

size_type count ( const key_type& k ) const;

cout << um1.count("搅拌车") << endl;

1. pair<iterator,bool> insert ( const value_type& val );//插入元素，成功返回的pair的第二个元素为true，失败则为false
2. iterator insert ( const_iterator hint, const value_type& val );//返回插入元素的位置
3. template <class InputIterator>
4. void insert ( InputIterator first, InputIterator last );//插入一段区间
5. void insert ( initializer_list<value_type> il );//将列表作为元素插入容器中

1.  cout << um1.insert(make_pair<string, int>("大货车", 9)).second << endl;//不存在，插入成功
2.  cout << um1.insert(make_pair<string, int>("搅拌车", 1)).second << endl;//已存在，插入失败

cout << um1.insert(um1.begin(), make_pair<string, int>("扫地车", 10))->second << endl;

1. unordered_map<string, int> um2(um1.begin(), um1.end());
2.  unordered_map<string, int>::iterator it2 = um2.begin();
3. 
4.  while (it2 != um2.end())
5.  {
6.    cout << it2->first << ":" << it2->second << endl;
7.    it2++;
8.  }
9.  cout << endl;

1.     unordered_map<string, int> um3;    
2.     um3.insert({ { "摩托车",3 }, { "电动车",7 }});
3.  unordered_map<string, int>::iterator it3 = um3.begin();
4.  while (it3 != um3.end())
5.  {
6.    cout << it3->first << ":" << it3->second << endl;
7.    it3++;
8.  }
9.  cout << endl;

1. iterator erase ( const_iterator position );//删除position位置的元素，并返回删除元素的位置
2. size_type erase ( const key_type& k );//返回删除值为k的元素的个数
3. iterator erase ( const_iterator first, const_iterator last );//删除从first到last区间的元素，并返回删除的last元素的位置

cout << um1.erase(um1.find("搅拌车"))->first << endl;

cout << um1.erase("自行车") << endl;

cout << um1.erase(um1.find("消防车"), um1.find("扫地车"))->first << endl;

void clear() noexcept;

um1.clear();

1.  unordered_map<string, string> um4;
2.  um4.insert(make_pair<string, string>("spring", "春天"));
3.  um4.insert(make_pair<string, string>("summer", "夏天"));
4.  um4.insert(make_pair<string, string>("autumn", "秋天"));
5.  um4.insert(make_pair<string, string>("winter", "冬天"));
6. 
7.  unordered_map<string, string> um5;
8.  um5.insert(make_pair<string, string>("east", "东"));
9.  um5.insert(make_pair<string, string>("south", "南"));
10.   um5.insert(make_pair<string, string>("west", "西"));
11.   um5.insert(make_pair<string, string>("north", "北"));
12. 
13.   um4.swap(um5);
14. 
15.   unordered_map<string, string>::iterator it4 = um4.begin();
16.   while (it4 != um4.end())
17.   {
18.     cout << it4->first << ":" << it4->second << endl;
19.     it4++;
20.   }
21.   cout << endl;
22. 
23.   unordered_map<string, string>::iterator it5 = um5.begin();
24.   while (it5 != um5.end())
25.   {
26.     cout << it5->first << ":" << it5->second << endl;
27.     it5++;
28.   }
29.   cout << endl;