STL学习（一）

一边看侯捷老师（STL源码分析）课程，一边记录下来，仅是给自己当笔记看的。

1. 认识headers,版本，重要资源

GP（Generic Programming）泛型编程，就是用模板（template）为主要工具来编写程序。STL正是泛型编程最成功的作品。

headers:

版本影响：几乎无影响，不同的编译器vc++6.0/dev-c++5.11 所带的标准版几乎无差别。

重要资源：CPlusPlus.com CppReference.com gcc.gnu.org(里面由标准库详细的函数，使用用法等，可以方便查找如何使用。) 书籍：STL源码剖析 / THE C++ STANDARD LIBRARY

2.STL体系结构基础介绍

总结：数据是存放在容器（class，模板类）里的，容器帮我们分配内存，这一操作需要分配器的支持，然后算法通过迭代器（迭代器类似于一个泛化指针）去操作容器，我们自己创造的一些法则，需要相加相减等就需要仿函数，适配器就是对容器，迭代器，仿函数可以做一下转化适配。

输出数组里大于等于40的数量：

前闭后开原则：所有的容器都遵循前闭后开，begin()指向第一个元素-[,end()指向最后一个元素-）。所以拿最后一个end()返回的泛化指针取引用其实是不存在的，所以遍历容器的话是以下写法：

c++11后新的写法（推荐）：

auto的使用：

3.容器的结构与分类（一）

序列式容器，关联式容器（key-value 快速查找）- 不定序容器（Hashtable） 红色标注的是c++11加的内容

附注：

其实标准库并没有规定set/map用什么实现，但由于红黑树的性能很好，所以各家编译器所带的标准库所用的就是红黑树。

测试程序之 辅助函数

using std::cin;
using std::cout;
using std::string;

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, "%d", 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;  
}

调用以上代码，测试array的性能

#include <array>
#include <iostream>
#include <ctime> 
#include <cstdlib> //qsort, bsearch, NULL

namespace jj01
{
void test_array()
{
	cout << "\ntest_array().......... \n";
     
array<long,ASIZE> c;  	
			
clock_t timeStart = clock();									
    for(long i=0; i< ASIZE; ++i) {
        c[i] = rand(); 
    }
	cout << "milli-seconds : " << (clock()-timeStart) << endl;	//
	cout << "array.size()= " << c.size() << endl;		
	cout << "array.front()= " << c.front() << endl;	
	cout << "array.back()= " << c.back() << endl;	
	cout << "array.data()= " << c.data() << endl;	
	
long target = get_a_target_long();

	timeStart = clock();
    ::qsort(c.data(), ASIZE, sizeof(long), compareLongs);//排序
long* pItem = (long*)::bsearch(&target, (c.data()), ASIZE, sizeof(long), compareLongs); 
	cout << "qsort()+bsearch(), milli-seconds : " << (clock()-timeStart) << endl;	//    
  	if (pItem != NULL)
    	cout << "found, " << *pItem << endl;
  	else
    	cout << "not found! " << endl;	
}
}

执行结果：

测试vector的性能 vector:在空间使用不足时，会寻找其他一份足够空间进行复制倍数增长，是一块连续的内存空间。 所以成倍增长，很可能造成浪费，所以查找速度快，但插入慢。

#include <vector>
#include <stdexcept>
#include <string>
#include <cstdlib> //abort()
#include <cstdio>  //snprintf()
#include <iostream>
#include <ctime> 
#include <algorithm> 	//sort()
namespace jj02
{
void test_vector(long& value)
{
	cout << "\ntest_vector().......... \n";
     
vector<string> c;  	
char buf[10];
			
clock_t timeStart = clock();								
    for(long i=0; i< value; ++i)
    {
    	try {
    		snprintf(buf, 10, "%d", rand());
        	c.push_back(string(buf));     		
		}
		catch(exception& p) {
			cout << "i=" << i << " " << p.what() << endl;	
			     //曾經最高 i=58389486 then std::bad_alloc
			abort();
		}
	}
	cout << "milli-seconds : " << (clock()-timeStart) << endl;	
	cout << "vector.max_size()= " << c.max_size() << endl;	//1073747823
	cout << "vector.size()= " << c.size() << endl;		
	cout << "vector.front()= " << c.front() << endl;	
	cout << "vector.back()= " << c.back() << endl;	
	cout << "vector.data()= " << c.data() << endl;
	cout << "vector.capacity()= " << c.capacity() << endl << endl;		

																				
string target = get_a_target_string();
//比较find和先sort后bsearch（二分查找）两种查找方式的速度
    {
	timeStart = clock();
auto pItem = find(c.begin(), c.end(), target);
	cout << "std::find(), milli-seconds : " << (clock()-timeStart) << endl;  
	 
  	if (pItem != c.end())
    	cout << "found, " << *pItem << endl << endl;
  	else
    	cout << "not found! " << endl << endl;
    }

	{
	timeStart = clock();
    sort(c.begin(), c.end());
	cout << "sort(), milli-seconds : " << (clock()-timeStart) << endl; 
	
	timeStart = clock();	    
string* pItem = (string*)::bsearch(&target, (c.data()), 
                                   c.size(), sizeof(string), compareStrings); 
	cout << "bsearch(), milli-seconds : " << (clock()-timeStart) << endl; 
	   
  	if (pItem != NULL)
    	cout << "found, " << *pItem << endl << endl;
  	else
    	cout << "not found! " << endl << endl;	
	}
	
	c.clear();
	test_moveable(vector<MyString>(),vector<MyStrNoMove>(), value);	
}	
}

执行结果：

测试list的性能 list:每个数据都是一块独立的内存空间，所以是不连续的内存空间。内存利用率好，所以插入快，但是查找速度慢。

#include <list>
#include <stdexcept>
#include <string>
#include <cstdlib> //abort()
#include <cstdio>  //snprintf()
#include <algorithm> //find()
#include <iostream>
#include <ctime> 
namespace jj03
{
void test_list(long& value)
{
	cout << "\ntest_list().......... \n";
     
list<string> c;  	
char buf[10];
			
clock_t timeStart = clock();							
    for(long i=0; i< value; ++i)
    {
    	try {
    		snprintf(buf, 10, "%d", rand());
        	c.push_back(string(buf));    	
		}
		catch(exception& p) {
			cout << "i=" << i << " " << p.what() << endl;	
			abort();
		}
	}
	cout << "milli-seconds : " << (clock()-timeStart) << endl;		
	cout << "list.size()= " << c.size() << endl;
	cout << "list.max_size()= " << c.max_size() << endl;    //357913941
	cout << "list.front()= " << c.front() << endl;	
	cout << "list.back()= " << c.back() << endl;		
		
string target = get_a_target_string();		
    timeStart = clock();		
auto pItem = find(c.begin(), c.end(), target);						
	cout << "std::find(), milli-seconds : " << (clock()-timeStart) << endl;		
	
  	if (pItem != c.end())
    	cout << "found, " << *pItem << endl;
  	else
    	cout << "not found! " << endl;	
    	
    timeStart = clock();		
	c.sort();//标准库有sort(),容器自己也有sort(),一般容器内的较快						
	cout << "c.sort(), milli-seconds : " << (clock()-timeStart) << endl;		    	
    	
	c.clear();
	test_moveable(list<MyString>(),list<MyStrNoMove>(), value);								
}	
}

执行结果：

测试forward_list的性能

#include <forward_list>
#include <stdexcept>
#include <string>
#include <cstdlib> //abort()
#include <cstdio>  //snprintf()
#include <iostream>
#include <ctime> 
namespace jj04
{
void test_forward_list(long& value)
{
	cout << "\ntest_forward_list().......... \n";
     
forward_list<string> c;  	
char buf[10];
			
clock_t timeStart = clock();								
    for(long i=0; i< value; ++i)
    {
    	try {
    		snprintf(buf, 10, "%d", rand());
        	c.push_front(string(buf));  //因为是单向链表，所以只能单向插入			   		
		}
		catch(exception& p) {
			cout << "i=" << i << " " << p.what() << endl;	
			abort();
		}
	}
	cout << "milli-seconds : " << (clock()-timeStart) << endl;	
	cout << "forward_list.max_size()= " << c.max_size() << endl;  //536870911
	cout << "forward_list.front()= " << c.front() << endl;	


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

执行结果：

使用容器deque： 分段连续

测试：

#include <deque>
#include <stdexcept>
#include <string>
#include <cstdlib> //abort()
#include <cstdio>  //snprintf()
#include <iostream>
#include <ctime> 
namespace jj05
{
void test_deque(long& value)
{
	cout << "\ntest_deque().......... \n";
     
deque<string> c;  	
char buf[10];
			
clock_t timeStart = clock();								
    for(long i=0; i< value; ++i)
    {
    	try {
    		snprintf(buf, 10, "%d", rand());
        	c.push_back(string(buf));    			 		
		}
		catch(exception& p) {
			cout << "i=" << i << " " << p.what() << endl;	
			abort();
		}
	}
	cout << "milli-seconds : " << (clock()-timeStart) << endl;		
	cout << "deque.size()= " << c.size() << endl;
	cout << "deque.front()= " << c.front() << endl;	
	cout << "deque.back()= " << c.back() << endl;	
	cout << "deque.max_size()= " << c.max_size() << endl;	//1073741821	
	
string target = get_a_target_string();	
    timeStart = clock();			
auto pItem = find(c.begin(), c.end(), target);	
	cout << "std::find(), milli-seconds : " << (clock()-timeStart) << endl;	
	
	if (pItem != c.end())
    	cout << "found, " << *pItem << endl;
  	else
    	cout << "not found! " << endl;	
    	
    timeStart = clock();		
	sort(c.begin(), c.end());						
	cout << "sort(), milli-seconds : " << (clock()-timeStart) << endl;		
	
	c.clear();
	test_moveable(deque<MyString>(),deque<MyStrNoMove>(), value);		 						
}															
}

执行结果：

使用容器stack/queue：(其实容器deque就包含了这两个)

使用容器multiset：(重复的也会放进去)

#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);	 						
}															 
}

执行结果：

使用容器multimap：

#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();		  					
}															 
}

执行结果：

使用容器unordered_multiset-hash_multiset：(每个篮子数据不会太长，当其中一个篮子的数量多余篮子总数是，就会倍数增长篮子数，然后打散数据重新挂在篮子上，所以篮子的数量一定会比篮子数据多)

#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);		 	 							
}													 
}

执行结果：

使用容器unordered_multimap-hash_multimap：

使用容器set：

#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;	
 	}							
}															 
}

使用容器map：

#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();					
}															 
}

4.使用分配器

视频地址