侯捷STL学习(二)

时间：2022-03-17 23:49:53

第六节：容器之分类和各种测试（四）

  • stack不提供iterator操作，破坏了容器的独特性，先进先出。

使用容器multiset（允许元素重复）

  • 内部是红黑树，insert操作就保证了排好了序。
  • 标准库有个：：find()函数，大家都可以用。容器本身也有一个c.find()，通过键值对查找非常快！
  • 测试
#include <set>

#include <stdexcept>

#include <string>

#include <cstdlib> //abort()

#include <cstdio>  //snprintf()

#include <iostream>

#include <ctime>

namespace jj06

{

void test_multiset(long& value)

{

	cout << "\ntest_multiset().......... \n";

multiset<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 << "multiset.size()= " << c.size() << endl;

	cout << "multiset.max_size()= " << c.max_size() << endl;	//214748364

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;

 	}	

	c.clear();

	test_moveable(multiset<MyString>(),multiset<MyStrNoMove>(), value);

}

}

使用容器multimap（允许元素重复）

  • 内部是红黑树，key-value键值对。
  • multiset不可用[]做insertion
  • c.insert(pair<long,string>(i,buff))
  • (*pItem).second
  • 测试
#include <map>

#include <stdexcept>

#include <string>

#include <cstdlib> //abort()

#include <cstdio>  //snprintf()

#include <iostream>

#include <ctime>

namespace jj07

{

void test_multimap(long& value)

{

	cout << "\ntest_multimap().......... \n";

multimap<long, string> c;

char buf[10];

clock_t timeStart = clock();

    for(long i=0; i< value; ++i)

    {

    	try {

    		snprintf(buf, 10, "%d", rand());

    		//multimap 不可使用 [] 做 insertion

        	c.insert(pair<long,string>(i,buf));

		}

		catch(exception& p) {

			cout << "i=" << i << " " << p.what() << endl;

			abort();

		}

	}

	cout << "milli-seconds : " << (clock()-timeStart) << endl;

	cout << "multimap.size()= " << c.size() << endl;

	cout << "multimap.max_size()= " << c.max_size() << endl;	//178956970	

long target = get_a_target_long();

    timeStart = clock();

auto pItem = c.find(target);

	cout << "c.find(), milli-seconds : " << (clock()-timeStart) << endl;

	if (pItem != c.end())

    	cout << "found, value=" << (*pItem).second << endl;

  	else

    	cout << "not found! " << endl;	  

	c.clear();

}

}

使用unordered_multiset容器

  • 使用hashtable使用分离链地址方法实现
  • gnu C之前的名称hash_multiset
  • unorder_multiset.bucket_count篮子的个数
  • load_factor,max_load_factor,max_bucket_count方法
  • 篮子后面的链表不能太长，元素的个数大于等于篮子的个数，就需要重新分配篮子的大小，重新进行插入元素
  • c.find()容器自身的find操作快很多
  • 测试
#include <unordered_set>

#include <stdexcept>

#include <string>

#include <cstdlib> //abort()

#include <cstdio>  //snprintf()

#include <iostream>

#include <ctime>

namespace jj08

{

void test_unordered_multiset(long& value)

{

	cout << "\ntest_unordered_multiset().......... \n";

unordered_multiset<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_multiset.size()= " << c.size() << endl;

	cout << "unordered_multiset.max_size()= " << c.max_size() << endl;	//357913941

	cout << "unordered_multiset.bucket_count()= " << c.bucket_count() << endl;

	cout << "unordered_multiset.load_factor()= " << c.load_factor() << endl;

	cout << "unordered_multiset.max_load_factor()= " << c.max_load_factor() << endl;

	cout << "unordered_multiset.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;

 	}		

    c.clear();

	test_moveable(unordered_multiset<MyString>(),unordered_multiset<MyStrNoMove>(), value);

}

}

使用unordered_multimap容器

  • 测试
#include <unordered_map>

#include <stdexcept>

#include <string>

#include <cstdlib> //abort()

#include <cstdio>  //snprintf()

#include <iostream>

#include <ctime>

namespace jj09

{

void test_unordered_multimap(long& value)

{

	cout << "\ntest_unordered_multimap().......... \n";

unordered_multimap<long, string> c;

char buf[10];

clock_t timeStart = clock();

    for(long i=0; i< value; ++i)

    {

    	try {

    		snprintf(buf, 10, "%d", rand());

			//multimap 不可使用 [] 進行 insertion

			c.insert(pair<long,string>(i,buf));

		}

		catch(exception& p) {

			cout << "i=" << i << " " << p.what() << endl;

			abort();

		}

	}

	cout << "milli-seconds : " << (clock()-timeStart) << endl;

	cout << "unordered_multimap.size()= " << c.size() << endl;

	cout << "unordered_multimap.max_size()= " << c.max_size() << endl;	//357913941	

long target = get_a_target_long();

    timeStart = clock();

auto pItem = c.find(target);

	cout << "c.find(), milli-seconds : " << (clock()-timeStart) << endl;

	if (pItem != c.end())

    	cout << "found, value=" << (*pItem).second << endl;

  	else

    	cout << "not found! " << endl;

}

}

使用set容器

  • 不允许元素重复
#include <set>

#include <stdexcept>

#include <string>

#include <cstdlib> //abort()

#include <cstdio>  //snprintf()

#include <iostream>

#include <ctime>

namespace jj13

{

void test_set(long& value)

{

	cout << "\ntest_set().......... \n";

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 << "set.size()= " << c.size() << endl;

	cout << "set.max_size()= " << c.max_size() << endl;	   //214748364

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;

 	}

}

}

使用map容器

  • 不允许元素键重复
  • c[i]=string(buf)组成pair，允许这样进行插入操作
#include <map>

#include <stdexcept>

#include <string>

#include <cstdlib> //abort()

#include <cstdio>  //snprintf()

#include <iostream>

#include <ctime>

namespace jj14

{

void test_map(long& value)

{

	cout << "\ntest_map().......... \n";

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);

		}

		catch(exception& p) {

			cout << "i=" << i << " " << p.what() << endl;

			abort();

		}

	}

	cout << "milli-seconds : " << (clock()-timeStart) << endl;

	cout << "map.size()= " << c.size() << endl;

	cout << "map.max_size()= " << c.max_size() << endl;		//178956970

long target = get_a_target_long();

    timeStart = clock();

auto pItem = c.find(target);

	cout << "c.find(), milli-seconds : " << (clock()-timeStart) << endl;

	if (pItem != c.end())

    	cout << "found, value=" << (*pItem).second << endl;

  	else

    	cout << "not found! " << endl;			

    c.clear();

}

}

使用unorder_set容器

#include <unordered_set>

#include <stdexcept>

#include <string>

#include <cstdlib> //abort()

#include <cstdio>  //snprintf()

#include <iostream>

#include <ctime>

namespace jj15

{

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;

	cout << "unordered_set.max_size()= " << c.max_size() << endl;  //357913941

	cout << "unordered_set.bucket_count()= " << c.bucket_count() << endl;

	cout << "unordered_set.load_factor()= " << c.load_factor() << endl;

	cout << "unordered_set.max_load_factor()= " << c.max_load_factor() << endl;

	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;

 	}

}

}

使用unorder_map容器

#include <unordered_map>

#include <stdexcept>

#include <string>

#include <cstdlib> //abort()

#include <cstdio>  //snprintf()

#include <iostream>

#include <ctime>

namespace jj16

{

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);

		}

		catch(exception& p) {

			cout << "i=" << i << " " << p.what() << endl;

			abort();

		}

	}

	cout << "milli-seconds : " << (clock()-timeStart) << endl;

	cout << "unordered_map.size()= " << c.size() << endl;	//357913941

	cout << "unordered_map.max_size()= " << c.max_size() << endl;	

long target = get_a_target_long();

    timeStart = clock();

//! auto pItem = find(c.begin(), c.end(), target);	//map 不適用 std::find()

auto pItem = c.find(target);

	cout << "c.find(), milli-seconds : " << (clock()-timeStart) << endl;

	if (pItem != c.end())

    	cout << "found, value=" << (*pItem).second << endl;

  	else

    	cout << "not found! " << endl;

}

}

hash_set/hash_map/hash_multiset/hash_multimap

  • 包含gnu C的编译器就可以

  • 包含的头文件可能需要修改#include<...>非标准容器，由于时间的原因，没有放在一起,在C++11大会之前就出现了！

  • 测试

/*

以下測試 hash_multiset, hash_multimap 過程中遇到阻礙：

headers <hash_set> 和 <hash_map> 各有兩個，

分別在 ...\4.9.2\include\c++\backward 和 ...\4.9.2\include\c++\ext，

不知要用哪一組!

用 <ext\...> 那一組會有問題

   ...\4.9.2\include\c++\backward\hashtable.h

   [Error] no match for call to '(const hasher {aka const __gnu_cxx::hash<std::basic_string<char> >}) (const key_type&)'

用 <backward\...> 那一組有相同的問題.

so, 放棄測試 (no insertion or push_back or ...).

*/

#include <ext\hash_set>

    //...\4.9.2\include\c++\backward\backward_warning.h

	//[Warning] #warning This file includes at least one deprecated or antiquated header

	//which may be removed without further notice at a future date.

	//Please use a non-deprecated interface with equivalent functionality instead.

	//For a listing of replacement headers and interfaces, consult the file backward_warning.h.

	//To disable this warning use -Wno-deprecated. [-Wcpp]

#include <stdexcept>

#include <string>

#include <cstdlib> //abort()

#include <cstdio>  //snprintf()

#include <iostream>

#include <ctime>

namespace jj11

{

void test_hash_multiset(long& value)

{

	cout << "\ntest_hash_multiset().......... \n";

	__gnu_cxx::hash_multiset<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;

}

}

//---------------------------------------------------

#include <ext\hash_map>

    //...\4.9.2\include\c++\backward\backward_warning.h

	//[Warning] #warning This file ... (如上個函數所言)

#include <stdexcept>

#include <string>

#include <cstdlib> //abort()

#include <cstdio>  //snprintf()

#include <iostream>

#include <ctime>

namespace jj12

{

void test_hash_multimap(long& value)

{

	cout << "\ntest_hash_multimap().......... \n";

	__gnu_cxx::hash_multimap<long, string> c;

	char buf[10];

    clock_t timeStart = clock();

    for(long i=0; i< value; ++i)

    {

    	try {

    		snprintf(buf, 10, "%d", rand());

        	//c.insert(...

		}

		catch(exception& p) {

			cout << "i=" << i << " " << p.what() << endl;

			abort();

		}

	}

	cout << "milli-seconds : " << (clock()-timeStart) << endl;		

    timeStart = clock();

    //! auto ite = c.find(...

	cout << "milli-seconds : " << (clock()-timeStart) << endl;

}

}

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