unordered_map和map的第⼀个差异是对key的要求不同,map要求Key⽀持⼩于⽐较,而unordered_map要求Key⽀持转成整形且⽀持等于⽐较,要理解unordered_map的这个两点要求得后续我们结合哈希表底层实现才能真正理解,也就是说这本质是哈希表的要求。 unordered_map和map的第⼆个差异是迭代器的差异,map的itera...
1 unordered_map<Key,T>::iterator it; 2 (*it).first; // the key value (of type Key) 3 (*it).second; // the mapped value (of type T) 4 (*it); // the "element value" (of type pair<const Key,T>) 它的键值分别是迭代器的first和second属性。 1 it->first; // same as ...
#include <iostream>#include <map>int main() {// 创建并初始化一个mapstd::map<std::string, int> m = { {"Alice", 25}, {"Bob", 22}, {"Charlie", 30} };// 插入元素// std::pair<iterator,bool> insert (const value_type& val);m.insert(std::make_pair("David", 32));// 查找...
unordered_map<char, int> Mymap; int main() { Mymap c1; c1.insert(Mymap::value_type('a', 1)); c1.insert(Mymap::value_type('b', 2)); c1.insert(Mymap::value_type('c', 3)); // display contents " [c 3] [b 2] [a 1]" for (Mymap::const_iterator it = c1.begin...
{"Linux 教程","http://c.biancheng.net/linux/"} };unordered_map<string, string>::iterator iter = umap.find("Python 教程");unordered_map<string, string>::iterator iter2 = umap.find("GO 教程");// 查找失败if(iter2 == umap.end())cout <<"当前容器中没有以\"GO 教程\"为键的键值对...
empty (1)explicit unordered_map ( size_type n = /* see below */,const hasher& hf = hasher(),const key_equal& eql = key_equal(),const allocator_type& alloc = allocator_type() );explicit unordered_map ( const allocator_type& alloc );range (2)template <class InputIterator>unordered_...
autoiter=people.emplace_hint(pr.first,"F",67);// Returns iterator people.emplace_hint(iter,std::make_pair("G",59));//Uses converting pair<string, size_t> // 初始化时,设定容器容量 size_tmax_element_count{100}; people.reserve(max_element_count); ...
insert(45); multiset<int>::iterator it, it1, it2; cout << "Multiset elements after sort" << endl; for (it = s.begin(); it != s.end(); it++) cout << *it << ' '; cout << endl; it1 = s.find(10); it2 = s.find(90); s.erase(it1, it2); cout << "Multiset ...
map<char, int>::iterator it = map1.begin(); map1.insert(it, pair<char, int>('x', 100)); 插入range 代码语言:javascript 复制 map<char, int> map2; map2.insert(map1.begin(), map1.find('c')); erase有三种用法: 通过key删除某个元素 代码语言:javascript 复制 map1.erase('a'); 通...
#include <unordered_map> #include <vector> #include <algorithm> // for std::copy #include <iterator> // for std::inserter int main() { std::vector<std::pair<char, int>> vec = {{'a', 1}, {'b', 2}, {'c', 3}}; std::unordered_map<char, int> m; // 使用 std::copy ...