侯捷STL學習(一)--順序容器測試

時間  2019-11-18
標籤 stl 學習 順序 容器 測試 简体版
原文   原文鏈接
  • 開始跟着《STL源碼剖析》的做者侯捷真人視頻，學習STL,瞭解STL背後的真實故事！
  • 視頻連接：侯捷STL
  • 還有很大其餘視頻須要的留言

第一節：STL版本和重要資源

  • STL和標準庫的區別

第二節：STL六大部件

  • 迭代器將容器和算法結合起來
  • 分配器實現，適配器用的地方不少

  • 實例：

  • 理解容器的前閉後開的設計。迭代器相似於指針，不少操做和指針差很少++,--運算。vec.begin(),vec.end()指向容器最後一個元素的下一個位置，解引用*（vec.end()）錯誤！
  • auto關鍵字的應用
std::vector<double> vec;
for(auto elem: vec)
{
   std::cout<<elem<<std::endl;
}

第三節：容器之分類和各類測試（一）

分類結構

  • 紅色框中標註的是C++11開始有的容器
  • Array數組容器，大小固定的
  • Deque:兩段均可以進行插入刪除操做，可是從內存上講不通，怎麼實現的要從後面的學習知道。
  • List:是一個雙向的循環鏈表，注意是雙向的。
  • Forward-List:單向鏈表，當能用單向鏈表的時候儘可能用，能夠減小內存空間，一個指針在32位pc上佔4個字節，當數據量不少上百萬，不可忽略！
  • Set鍵值都同樣，MultiSet容許元素有重複。
  • Set/Map用紅黑樹實現，RB-tree是自平衡的二叉樹。
  • Unorder Containers:是C++標準庫裏賣的內容。
  • 根據這些圖例，能夠知道這些容器在內存用到的數據結構是什麼樣的。
  • HashTable實現方法不少，但基本都用Separate Chaining(分離鏈地址法實現)。

測試Array

  • 指針void* a -> *(long*)a;
  • array<long, size> c使用初始化大小，#include<array>
  • c.data()返回這個數組的初始地址，和數組的地址對比
  • qsort應用：qsort(c.data,size,size(long),comparelongs)
  • bsearch()應用,查找前必須排好序了：bsearch(&target,(c.data()),size,size(long),comparelongs)
  • qsort,bsearch包含頭文件#include<cstdlib>，C自己庫函數
#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;  
}
}

第四節：容器之分類和各類測試（二）

測試Vector

  • 主要經過程序細節說明
  • namespace命名空間的說明
  • vector的增加速度是2倍增加，當capacity不夠時，容量增加爲前面的2倍。是在另外的2倍空間！
  • try...catch...捕獲函數，字符串最大佔一個指針大小，空間不夠的時候拋出，abort()退出
  • ::find()模板函數，加冒號代表是全局函數，當沒有冒號時，編譯器在當前沒有找到，也會到全局去找。
  • 用兩種查找算法比較，find()用時更少。
#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); 
}   
}

第五節：容器之分類和各類測試（三）

測試List，雙向鏈表

  • list.max_size()按理list是動態申請空間的，爲何最大的size呢？
  • list雙向鏈表實現
  • 有趣的c.sort(),這裏注意在STL標準庫全局有一個sort函數，但這裏調用的是list容器自身內部的sort函數。注意在STL容器中有些自身有sort函數，此時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);                             
}   
}

測試forward-list，單向鏈表

  • forward-list單向鏈表，C++11出現的
  • push_front在鏈表頭插入，不提供在尾部插入，效率低些。
  • front取鏈表頭的元素，不提供back()操做取鏈表尾的元素。
  • 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();   
}                                            
}

測試slist

  • Gnu C以前的單鏈表,forward-list是C++11纔出現的
  • #include<ext\slist>頭文件
#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;          
}                                                           
}

測試deque

  • 雙向開口，是分段連續，感受是連續的，其實不是。
  • 內存上兩邊均可以擴充
  • 每次512擴充，兩邊擴充申請buffer,buffer由指針指向
  • 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);                               
}                                                           
}

測試stack

  • 棧,數據結構上和deque差很少
  • 兩段插入插入刪除受限的容器
  • 也有人叫作容器的適配器adapter
  • 沒有提供容器的迭代器iterator,不然對迭代器的操做會破壞堆棧的結構
  • 也沒有提供find,sort的功能；可是有時候讓你實現堆棧的排序操做

#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> >'
        
}                                                           
}

測試queue

  • 堆，數據結構上有deque衍生出來的
  • 沒有提供容器的迭代器iterator,不然對迭代器的操做會破壞堆棧的結構

#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> >'  
}                                                           
}
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