侯捷STL学习(一)

• 开始跟着《STL源码剖析》的作者侯捷真人视频，学习STL,了解STL背后的真实故事！
• 视频链接：侯捷STL
• 还有很大其他视频需要的留言

第一节：STL版本和重要资源

• STL和标准库的区别

• 三个网站
  • CPlusPlus
  • CppReference
  • gcc.gnu.org
  • Boost

第二节：STL六大部件

• 迭代器将容器和算法结合起来
• 分配器实现，适配器用的地方很多

• 实例：

• 理解容器的前闭后开的设计。迭代器类似于指针，很多操作和指针差不多++,--运算。vec.begin(),vec.end()指向容器最后一个元素的下一个位置，解引用*（vec.end()）错误！
• auto关键字的应用

std::vector<double> vec;
for(auto elem: vec)
{
   std::cout<<elem<<std::endl;
}

第三节：容器之分类和各种测试（一）

分类结构

• 红色框中标注的是C++11开始有的容器
• Array数组容器，大小固定的
• Deque:两段都可以进行插入删除操作，但是从内存上讲不通，怎么实现的要从后面的学习知道。
• List:是一个双向的循环链表，注意是双向的。
• Forward-List:单向链表，当能用单向链表的时候尽量用，可以减少内存空间，一个指针在32位pc上占4个字节，当数据量很多上百万，不可忽略！
• Set键值都一样，MultiSet允许元素有重复。
• Set/Map用红黑树实现，RB-tree是自平衡的二叉树。
• Unorder Containers:是C++标准库里卖的内容。
• 根据这些图例，可以知道这些容器在内存用到的数据结构是什么样的。
• HashTable实现方法很多，但基本都用Separate Chaining(分离链地址法实现)。

测试Array

• 指针void* a -> *(long*)a;
• array<long, size> c使用初始化大小，#include<array>
• c.data()返回这个数组的初始地址，和数组的地址对比
• qsort应用：qsort(c.data,size,size(long),comparelongs)
• bsearch()应用,查找前必须排好序了：bsearch(&target,(c.data()),size,size(long),comparelongs)
• qsort,bsearch包含头文件#include<cstdlib>，C本身库函数

#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);
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;
}
}

第四节：容器之分类和各种测试（二）

测试Vector

• 主要通过程序细节说明
• namespace命名空间的说明
• vector的增长速度是2倍增长，当capacity不够时，容量增长为前面的2倍。是在另外的2倍空间！
• try...catch...捕获函数，字符串最大占一个指针大小，空间不够的时候抛出，abort()退出
• ::find()模板函数，加冒号表明是全局函数，当没有冒号时，编译器在当前没有找到，也会到全局去找。
• 用两种查找算法比较，find()用时更少。

#include <vector>
#include <stdexcept>
#include <string>
#include <cstdlib> //abort()   //qsort, bsearch, NULL
#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();
    {
	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);
}
}

第五节：容器之分类和各种测试（三）

测试List，双向链表

• list.max_size()按理list是动态申请空间的，为什么最大的size呢？
• list双向链表实现
• 有趣的c.sort(),这里注意在STL标准库全局有一个sort函数，但这里调用的是list容器自身内部的sort函数。注意在STL容器中有些自身有sort函数，此时用自身的排序算法更快。

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

	c.clear();
	test_moveable(list<MyString>(),list<MyStrNoMove>(), value);
}
}

测试forward-list，单向链表

• forward-list单向链表，C++11出现的
• push_front在链表头插入，不提供在尾部插入，效率低些。
• front取链表头的元素，不提供back()操作取链表尾的元素。
• c.sort()用它自身的排序算法

#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));
		}
		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();
}
}

测试slist

• Gnu C之前的单链表,forward-list是C++11才出现的
• #include<ext\slist>头文件

#include <ext\slist>
	//注意, 上一行並沒有引發警告訊息如 #include <ext\hash_set> 所引發者：
	//...\4.9.2\include\c++\backward\backward_warning.h
	//[Warning] ...

#include <stdexcept>
#include <string>
#include <cstdlib> //abort()
#include <cstdio>  //snprintf()
#include <iostream>
#include <ctime>
namespace jj10
{
void test_slist(long& value)
{
	cout << "\ntest_slist().......... \n";

	__gnu_cxx::slist<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));
		}
		catch(exception& p) {
			cout << "i=" << i << " " << p.what() << endl;
			abort();
		}
	}
	cout << "milli-seconds : " << (clock()-timeStart) << endl;
}
}

测试deque

• 双向开口，是分段连续，感觉是连续的，其实不是。
• 内存上两边都可以扩充
• 每次512扩充，两边扩充申请buffer,buffer由指针指向
• max_size由限制，使用全局的sort排序

#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);
}
}

测试stack

• 栈,数据结构上和deque差不多
• 两段插入插入删除受限的容器
• 也有人叫做容器的适配器adapter
• 没有提供容器的迭代器iterator,否则对迭代器的操作会破坏堆栈的结构
• 也没有提供find,sort的功能；但是有时候让你实现堆栈的排序操作

#include <stack>
#include <stdexcept>
#include <string>
#include <cstdlib> //abort()
#include <cstdio>  //snprintf()
#include <iostream>
#include <ctime>
namespace jj17
{
void test_stack(long& value)
{
	cout << "\ntest_stack().......... \n";

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

clock_t timeStart = clock();
    for(long i=0; i< value; ++i)
    {
    	try {
    		snprintf(buf, 10, "%d", rand());
        	c.push(string(buf));
		}
		catch(exception& p) {
			cout << "i=" << i << " " << p.what() << endl;
			abort();
		}
	}
	cout << "milli-seconds : " << (clock()-timeStart) << endl;
	cout << "stack.size()= " << c.size() << endl;
	cout << "stack.top()= " << c.top() << endl;
	c.pop();
	cout << "stack.size()= " << c.size() << endl;
	cout << "stack.top()= " << c.top() << endl;	

	{
stack<string, list<string>> c;		//以 list 為底層
    for(long i=0; i< 10; ++i) {
    		snprintf(buf, 10, "%d", rand());
        	c.push(string(buf));
	}
	cout << "stack.size()= " << c.size() << endl;
	cout << "stack.top()= " << c.top() << endl;
	c.pop();
	cout << "stack.size()= " << c.size() << endl;
	cout << "stack.top()= " << c.top() << endl;
    }	

	{
stack<string, vector<string>> c;	//以 vector 為底層
    for(long i=0; i< 10; ++i) {
    		snprintf(buf, 10, "%d", rand());
        	c.push(string(buf));
	}
	cout << "stack.size()= " << c.size() << endl;
	cout << "stack.top()= " << c.top() << endl;
	c.pop();
	cout << "stack.size()= " << c.size() << endl;
	cout << "stack.top()= " << c.top() << endl;
    }

	{
stack<string, set<string>> c;	//以 set 為底層
/*!
    for(long i=0; i< 10; ++i) {
    		snprintf(buf, 10, "%d", rand());
        	c.push(string(buf));
	}
	cout << "stack.size()= " << c.size() << endl;
	cout << "stack.top()= " << c.top() << endl;
	c.pop();
	cout << "stack.size()= " << c.size() << endl;
	cout << "stack.top()= " << c.top() << endl;	

//[Error] 'class std::set<std::basic_string<char> >' has no member named 'push_back'
//[Error] 'class std::set<std::basic_string<char> >' has no member named 'back'
//[Error] 'class std::set<std::basic_string<char> >' has no member named 'pop_back'
*/
    }

//!stack<string, map(string>> c5;	////以 map 為底層, [Error] template argument 2 is invalid
//!stack<string>::iterator ite1;  	//[Error] 'iterator' is not a member of 'std::stack<std::basic_string<char> >'

}
}

测试queue

• 堆，数据结构上有deque衍生出来的
• 没有提供容器的迭代器iterator,否则对迭代器的操作会破坏堆栈的结构

#include <queue>
#include <stdexcept>
#include <string>
#include <cstdlib> //abort()
#include <cstdio>  //snprintf()
#include <iostream>
#include <ctime>
namespace jj18
{
void test_queue(long& value)
{
	cout << "\ntest_queue().......... \n";

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

clock_t timeStart = clock();
    for(long i=0; i< value; ++i)
    {
    	try {
    		snprintf(buf, 10, "%d", rand());
        	c.push(string(buf));
		}
		catch(exception& p) {
			cout << "i=" << i << " " << p.what() << endl;
			abort();
		}
	}
	cout << "milli-seconds : " << (clock()-timeStart) << endl;
	cout << "queue.size()= " << c.size() << endl;
	cout << "queue.front()= " << c.front() << endl;
	cout << "queue.back()= " << c.back() << endl;
	c.pop();
	cout << "queue.size()= " << c.size() << endl;
	cout << "queue.front()= " << c.front() << endl;
	cout << "queue.back()= " << c.back() << endl;	

	{
queue<string, list<string>> c;		//以 list 為底層
    for(long i=0; i< 10; ++i) {
    		snprintf(buf, 10, "%d", rand());
        	c.push(string(buf));
	}
	cout << "queue.size()= " << c.size() << endl;
	cout << "queue.front()= " << c.front() << endl;
	cout << "queue.back()= " << c.back() << endl;
	c.pop();
	cout << "queue.size()= " << c.size() << endl;
	cout << "queue.front()= " << c.front() << endl;
	cout << "queue.back()= " << c.back() << endl;
    }	

	{
queue<string, vector<string>> c;	//以 vector 為底層
    for(long i=0; i< 10; ++i) {
    		snprintf(buf, 10, "%d", rand());
        	c.push(string(buf));
	}
	cout << "queue.size()= " << c.size() << endl;
	cout << "queue.front()= " << c.front() << endl;
	cout << "queue.back()= " << c.back() << endl;
	//!c.pop();  //[Error] 'class std::vector<std::basic_string<char> >' has no member named 'pop_front'
	cout << "queue.size()= " << c.size() << endl;
	cout << "queue.front()= " << c.front() << endl;
	cout << "queue.back()= " << c.back() << endl;
    }	

	{
queue<string, set<string>> c;		//以 set 為底層
/*!
    for(long i=0; i< 10; ++i) {
    		snprintf(buf, 10, "%d", rand());
        	c.push(string(buf));
	}
	cout << "queue.size()= " << c.size() << endl;
	cout << "queue.front()= " << c.front() << endl;
	cout << "queue.back()= " << c.back() << endl;
	c.pop();
	cout << "queue.size()= " << c.size() << endl;
	cout << "queue.front()= " << c.front() << endl;
	cout << "queue.back()= " << c.back() << endl;
//[Error] 'class std::set<std::basic_string<char> >' has no member named 'push_back'
//[Error] 'class std::set<std::basic_string<char> >' has no member named 'front'
//[Error] 'class std::set<std::basic_string<char> >' has no member named 'pop_front'
*/
    }

//! queue<string, map<string>> c5;	//以 map 為底層, [Error] template argument 2 is invalid
//! queue<string>::iterator ite1;  	//[Error] 'iterator' is not a member of 'std::queue<std::basic_string<char> >'
}
}