比较map、hash_map和unordered_map的执行效率以及内存占用情况 **/#include<sys/types.h>#include<unistd.h>#include<sys/time.h>#include<iostream>#include<fstream>#include<string>#include<map>#include<ext/hash_map>#include<tr1/unordered_map>usingnamespacestd;usingnamespace__gnu_cxx;usingnamespacestd...
比较map、hash_map和unordered_map的执行效率以及内存占用情况 **/#include<sys/types.h>#include<unistd.h>#include<sys/time.h>#include<iostream>#include<fstream>#include<string>#include<map>#include<ext/hash_map>#include<tr1/unordered_map>usingnamespacestd;usingnamespace__gnu_cxx;usingnamespacestd...
Is unordered_map faster than a map? In the best case and the average case scenario, an unordered_map is faster than a map because the best case and the average case time complexities of all the operations in an unordered_map (O(1)) are less than the time complexity for all the operat...
#include <unordered_map>#include <string>int main(){// 哈希表默认初始化// 函数原型:unordered_map();// 创建一个空的 unordered_map 容器std::unordered_map<std::string, int> umap1;// 使用列表初始化// 函数原型:unordered_map(initializer_list<value_type>);// 使用初始化列表创建 unordered_map...
So far I know, when we do not need the elements to be ordered, we should use unordered_map which is the case in this problem. So why std::map works better than std::unordered_map in terms of time complexity? Thanks for your patience!
Complexity Average case: linear insize. Worst case: quadratic insize. Iterator validity No changes. See also unordered_map::equal_range Get range of elements with specific key(public member function) unordered_map::operator= Assign content(public member function)...
Most times I use a map, I use either int or std::string as the key type; hence, I've got no problems with the definition of the hash function. The more I thought about it, the more I came to realize that I can't find any reason of using a std::map over...
History std::unordered_multimap Defined in header<unordered_map> template< classKey, classT, classHash=std::hash<Key>, classKeyEqual=std::equal_to<Key>, classAllocator=std::allocator<std::pair<constKey, T>> >classunordered_multimap;
Defined in header <unordered_map> template< class Key, class T, class Hash = std::hash<Key>, class KeyEqual = std::equal_to<Key>, class Allocator = std::allocator< std::pair<const Key, T> > > class unordered_multimap; (1) (since C++11) namespace pmr { template <class Key,...
// clearing unordered_map#include <iostream>#include <string>#include <unordered_map>intmain () { std::unordered_map<std::string,std::string> mymap = { {"house","maison"}, {"car","voiture"}, {"grapefruit","pamplemousse"} }; std::cout <<"mymap contains:";for(auto& x: mymap...