关于set和map的区别前面已经说过，这里仅是用hashtable将其实现，所以不做过多说明，直接看程序

unordered_set

#include<stdexcept>
#include<string>
#include<cstdlib>
#include<cstdio>
#include<algorithm>
#include<iostream>
#include<ctime>
#include<unordered_set>
using namespace std;
long get_a_target_long()
{
	long target = 0;
	cout<<"target(0~"<<RAND_MAX<<"):";
	cin>>target;
	return target;
}
string get_a_target_string()
{
	long target = 0;
	char buf[10];
	cout<<"target(0~"<<RAND_MAX<<"):";
	cin>>target;
	snprintf(buf, 10, "%ld", target);
	return string(buf);
}
int compareLongs(const void* a, const void* b)
{
	return (*(long*)a - *(long*)b);
}

int compareStrings(const void *a, const void *b)
{
	if(*(string*)a > *(string*)b)
		return 1;
	else if(*(string*)a < *(string*)b)
		return -1;
	else
		return 0;
}
void test_unordered_set(long& value)
{
	cout << "\ntest_unordered_set().......... \n";

	unordered_set<string> c;  	
	char buf[10];

	clock_t timeStart = clock();								
	for(long i=0; i< value; ++i)
	{
		try {
			snprintf(buf, 10, "%d", rand());
			c.insert(string(buf));    			 		
		}
		catch(exception& p) {
			cout << "i=" << i << " " << p.what() << endl;	
			abort();
		}
	}
	cout << "milli-seconds : " << (clock()-timeStart) << endl;		
	cout << "unordered_set.size()= " << c.size() << endl;	//元素个数
	cout << "unordered_set.max_size()= " << c.max_size() << endl;  //
	cout << "unordered_set.bucket_count()= " << c.bucket_count() << endl;//篮子个数	
	cout << "unordered_set.load_factor()= " << c.load_factor() << endl;	//负载
	cout << "unordered_set.max_load_factor()= " << c.max_load_factor() << endl;//最大负载	
	cout << "unordered_set.max_bucket_count()= " << c.max_bucket_count() << endl;	//		
	for (unsigned i=0; i< 20; ++i) {
		cout << "bucket #" << i << " has " << c.bucket_size(i) << " elements.\n";
	}			

	string target = get_a_target_string();	
	{
		timeStart = clock();
		auto pItem = find(c.begin(), c.end(), target);	//比 c.find(...) 慢很多	
		cout << "std::find(), milli-seconds : " << (clock()-timeStart) << endl;		
		if (pItem != c.end())
			cout << "found, " << *pItem << endl;
		else
			cout << "not found! " << endl;	
	}

	{
		timeStart = clock();		
		auto pItem = c.find(target);		//比 std::find(...) 快很多							
		cout << "c.find(), milli-seconds : " << (clock()-timeStart) << endl;		 
		if (pItem != c.end())
			cout << "found, " << *pItem << endl;
		else
			cout << "not found! " << endl;	
	}	
}			
int main()
{
	long int value;
	cout<<"how many elements: ";
	cin>>value;
	test_unordered_set(value);
	return 0;
}

 运行结果

 

 

unordered_map

#include<stdexcept>
#include<string>
#include<cstdlib>
#include<cstdio>
#include<algorithm>
#include<iostream>
#include<ctime>
#include<unordered_map>
using namespace std;
long get_a_target_long()
{
	long target = 0;
	cout<<"target(0~"<<RAND_MAX<<"):";
	cin>>target;
	return target;
}
string get_a_target_string()
{
	long target = 0;
	char buf[10];
	cout<<"target(0~"<<RAND_MAX<<"):";
	cin>>target;
	snprintf(buf, 10, "%ld", target);
	return string(buf);
}
int compareLongs(const void* a, const void* b)
{
	return (*(long*)a - *(long*)b);
}

int compareStrings(const void *a, const void *b)
{
	if(*(string*)a > *(string*)b)
		return 1;
	else if(*(string*)a < *(string*)b)
		return -1;
	else
		return 0;
}
void test_unordered_map(long& value)
{
	cout << "\ntest_unordered_map().......... \n";

	unordered_map<long, string> c;  	
	char buf[10];

	clock_t timeStart = clock();								
	for(long i=0; i< value; ++i)
	{
		try {
			snprintf(buf, 10, "%d", rand());
			c[i] = string(buf);  //特殊的插入方式		
		}
		catch(exception& p) {
			cout << "i=" << i << " " << p.what() << endl;	
			abort();
		}
	}
	cout << "milli-seconds : " << (clock()-timeStart) << endl;		
	cout << "unordered_map.size()= " << c.size() << endl;	//元素个数
	cout << "unordered_map.max_size()= " << c.max_size() << endl;	

	long target = get_a_target_long();		
	timeStart = clock();	

	auto pItem = c.find(target);//map 不用 std::find() 

	cout << "c.find(), milli-seconds : " << (clock()-timeStart) << endl;		 
	if (pItem != c.end())
		cout << "found, value=" << (*pItem).second << endl;
	else
		cout << "not found! " << endl;		
}	
int main()
{
	long int value;
	cout<<"how many elements: ";
	cin>>value;
	test_unordered_map(value);
	return 0;
}

 运行结果