#include<unordered_map>// 0. include the libraryintmain(){// 1. initialize a hash map
unordered_map<int,int> hashmap;// 2. insert a new (key, value) pair
hashmap.insert(make_pair(0,0));
hashmap.insert(make_pair(2,3));// 3. insert a new (key, value) pair or update the value of existed key
hashmap[1]=1;
hashmap[1]=2;// 4. get the value of a specific key
cout <<"The value of key 1 is: "<< hashmap[1]<< endl;// 5. delete a key
hashmap.erase(2);// 6. check if a key is in the hash mapif(hashmap.count(2)<=0){
cout <<"Key 2 is not in the hash map."<< endl;}// 7. get the size of the hash map
cout <<"the size of hash map is: "<< hashmap.size()<< endl;// 8. iterate the hash mapfor(auto it = hashmap.begin(); it != hashmap.end();++it){
cout <<"("<< it->first <<","<< it->second <<") ";}
cout <<"are in the hash map."<< endl;// 9. clear the hash map
hashmap.clear();// 10. check if the hash map is emptyif(hashmap.empty()){
cout <<"hash map is empty now!"<< endl;}}