前言：本课程是我看了侯捷老师的课程之后整理，为了避免忘记，故作此整理。只是对六大部件做一个简单的介绍，在第二讲中我们会观看它们的源代码做一个详细的讲解。
在本节最后的代码中，我用到了命名空间，主要是让我们写的程序比如类，对象，模板再封装起来，这样可以跟别人不会发生冲突。
面向对象和泛型编程的区别在于，面向对象这种编程技巧，鼓励我们把数据放在类里头，把处理数据的函数也放在类里头，而泛型编程却不一样，数据放在容器里头，而操作数据的都动作即算法则放在另一个类里面，所以其设计方式跟面向对象不一样。在GP中，容器和算法之间的桥梁是迭代器（iterators）,迭代器也是一种泛型指针。
如下幻灯片。
以上就是C++的六大部件，其中容器和算法最为重要，容器需要放东西，东西要占用内存，容器的好处是帮我们把内存的东西解决掉，所以其背后需要另外一个东西作支撑即分配器，容器外头是适配器，他是用来对某些容器做一些改造的，其次，容器需要算法来对数据进行操作，所以中间需要一个桥梁即迭代器。其次仿函数，仿函数可能是一个类，或者一个模板。
以下我们用一个简单的例子，来把以上的六大部件，全部用一遍。
在11行，vector就是一种容器，他里面用来放整型数据，后面的那个allocator,就是一个分配器，他用来分配内存，而count_if则是一个算法名称，他后面的vi.begin(),vi.end()就是迭代器，not1是一个函数适配器，表示对条件取反，bind2nd也是一个函数适配器，用来绑定第二参数40，less<int> (),则是一个仿函数，“()”则为一个临时对象，这些东西在后面都会在源代码中逐一讲解。
再来谈谈时间复杂度，时间复杂度中n,必须是那种很大的数，才有意义。
其次注意一个问题，前闭后开区间，如下所示，所以当我们用“*（c.end()）”来取值是会出错的。
容器分为序列式容器和关联式容器。如下所示
序列式容器有array即数组，array的空间是连续的，因此他可以随机存取，其实其大小固定，不能改变，就好像在数组中，我们必须制定数组的大小。Vector这种容器是从尾部插入元素，他也是连续空间，但是其大小不固定，他的大小是两倍增长，即当前空间放满元素之后，分配器会自动在另一个地方分配一个两倍大的空间，然后将当前数据元素，逐一拷贝到另外一个两倍大的空间，这些动作均可以在源代码中看到。其次Deque是一个分段连续的空间，在第二讲中再做详细讲解。其次List是一个双向链表，他并非连续空间，他是通过指针将空间中散落的点，串联起来，所以他不支持随机存取，但是其插入删除较快，其次forward_list是一个单向链表。其次再看关联式容器，关联式容器其底部由红黑树或者哈希表这种数据结构作支撑。像Unordered_containers其底部就是由哈希表做支撑，而另外的则是由红黑树做支撑。set是一个不允许元素重复的容器，其次因为其底部是由红黑书做支撑，所以它是有序的，multi_set则允许元素重复。map和multi_map,则是一个pair,他key和value组成，map不允许key重复，multi_map允许key重复，其次因为其底部为红黑树，所以其key为有序。像以红黑树，和哈希表做支撑的容器，适合用来查找，查找很快，所以这些容器会自带查找算法。
下面讲一下分配器，分配器一般不需要我们指定，编译器会自动制定，不同的编译器，分配器也差不多一样。所以即使我们会用，也不建议使用。如下所示。
在gnu c2.9中有很多非标准的分配器，之所以说非标准，是因为在他是gnu自己扩展的分配器，在VC或者BC中不存在。如下所示。如果非要使用非标准的分配器，则必须指定其命名空间，因为这些分配器并非在命名空间std当中，而是在__gnu_cxx这个命名空间里面。右边的那个__pool_alloc就是一个很著名的内存池结构，他在gnu2.9版本中就叫alloc,而在gnu_4.9中才叫__pool_alloc。
之所以不建议我们指定分配器，是因为有一个致命伤，他必须让我们记住用了多少内存，还的时候，还要我们告诉其用了多少内存，这样它才能回收，如下所示。
以下代码，是对所有容器的一个简单测试，输入的数据应是百万级别的规模，这样才有意义。
#include<iostream>
#include<string>
#include<cstdlib>
using std::cin;
using std::cout;
using std::string;
string get_a_target_string()
{
char buf[10];
long target = 0;
cout << "target (0~" << RAND_MAX << "):";
cin >> target;
snprintf(buf, 10, "%d", target);
return string(buf);
}
long get_a_target_long()
{
long target = 0;
cout << "target (0~" << RAND_MAX << "):";
cin >> target;
return target;
}
int compartLongs(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;
}
#include<array>
#include<iostream>
#include<ctime>
#include<cstdlib>
namespace jj01
{
//array数据结构为一个数组
using namespace std;
void test_array()
{
cout << "\ntest_array().............\n";
const long ASIZE = 100000;
array<long,ASIZE> c;
clock_t timeStart = clock();
for (long i = 0; i < ASIZE; i++)
{
c[i] = rand();
}
cout << "milll-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), compartLongs);
long* pItem = (long*)bsearch(&target, (c.data()), ASIZE, sizeof(long), compartLongs);
cout << "qsort()+bsearch(),milli-seconds : " << (clock() - timeStart) << endl;
if (pItem!=NULL)
{
cout << "found, " << *pItem << endl;
}
else
{
cout << "not found!" << endl;
}
}
}
#include<vector>
#include<stdexcept>
#include<string>
#include<cstdlib>
#include<cstdio>
#include<iostream>
#include<ctime>
#include<algorithm>
namespace jj02
{
using namespace std;
//vector的空间是两倍增长的尾部可以插入元素的数组
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 (const std::exception& p)
{
cout << "i=" << i << " " << p.what() << endl;
abort();
}
}
cout << "milll-seconds: " << (clock()-timeStart) << endl;
cout << "vector.size()= " << c.size() << endl; //size()真正元素的个数
cout << "vector.front()= " << c.front() << endl; //vector的第一个元素
cout << "vector.back()= " << c.back() << endl; //vector的最后一个元素
cout << "vector.data()= " << c.data() << endl; //呼叫整个vector的起始空间
cout << "vector.capacity()= " << c.capacity() << endl;//capacity()表示真正容量有多大
string target = get_a_target_string();
{
timeStart = clock();
auto pItem = find(c.begin(), c.end(), target);
cout << "::find(),mill-second:" << (clock() - timeStart) << endl;
if (pItem != c.end())
cout << "found, " << *pItem << endl;
else
cout << "not found" << endl;
}
timeStart = clock();
sort(c.begin(), c.end());
string* pItem = (string*)bsearch(&target, (c.data()), c.size(), sizeof(string), compareStrings);
cout << "sort()+bsearch(),milli-seconds: " << (clock()-timeStart) << endl;
if (pItem != NULL)
{
cout << "found, " << *pItem << endl;
}
else
{
cout << "not found!" << endl;
}
}
}
#include<iostream>
#include<list>
#include<string>
#include<algorithm>
#include<cstdlib>
#include<ctime>
namespace jj03
{
//list数据结构为一个双向链表
using namespace std;
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 (const std::exception& p)
{
cout << "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;
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 << "::find(),milli-seconds:" << (clock()-timeStart) << endl;
if (pItem != c.end())
{
cout << "found, " << *pItem << endl;
}
else
{
cout << "not found!" << endl;
}
timeStart = clock();
c.sort(); //list容器里面有自带的排序算法，所以我们选择自带的排序算法，效率比较高
cout << "c.sort(),mill-seconds:" << (clock() - timeStart) << endl;
}
}
#include<string>
#include<forward_list>
#include<ctime>
#include<cstdlib>
namespace jj04
{
//forward_list数据结构为单向链表
using namespace std;
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)); //注意forward_list只有push_front()放元素，没有push_back()方法
}
catch (const std::exception& p)
{
cout << "i=" << i << " " << p.what() << endl;
abort();
}
}
cout << "milli-seconds():" << (clock() - timeStart) << endl;
cout << "forward_list.max_size():" << c.max_size() << endl; //最多可以放多少个元素
cout << "forward_list.front():" << c.front() << endl;
//注意，forward_list没有back()方法，也没有size()方法
string target = get_a_target_string();
timeStart = clock();
auto pItem = find(c.begin(), c.end(), target);
cout <<"::find(),milli-seconds:" << (clock() - timeStart) << endl;
//这样写是不对的，因为pItem是一个迭代器，或者是泛型指针，但是不是指针，所以不可以这样写
//if (pItem != NULL)
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;
}
}
#include<deque>
namespace jj05
{
//deque数据结构为双端队列
using namespace std;
void test_deque(long& value)
{
cout << "\ntest_deque()...............";
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 (const std::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;
string target = get_a_target_string();
timeStart = clock();
auto pItem = find(c.begin(), c.end(), target);
cout << "::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;
}
}
#include<stack>
namespace jj06
{
using namespace std;
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 (const std::exception& p)
{
cout << "i:" << i << " " << p.what() << endl;
abort();
}
}
//因为这里是栈，所以不存在查找，排序以及插入等功能
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;
}
}
#include<queue>
namespace jj07
{
//queue数据结构为deque
using namespace std;
void test_queue(long& value)
{
cout << "test_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 (const std::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;
}
}
#include<unordered_map>
namespace jj08
{
//unordered_map的数据结构为哈希表
using namespace std;
void test_unordered_map(long& value)
{
cout << "\ntest_inordefed_map()..............";
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); //注意unordered_map插入元素的方法，i表示key，buf表示value
}
catch (const std::exception& p)
{
cout << "i:" << i << " " << p.what() << endl;
abort();
}
}
cout << "milli-seconds:" << (clock() - timeStart) << endl;
cout << "unordered_map.size():" << c.size() << endl;
cout << "unordered_map.max_size():" << c.max_size() << endl;
long target = get_a_target_long();
timeStart = clock();
//注意这里是调用unordered_map自己的查找方法，有自己的方法
//一定要用自己的查找方法
auto pItem = c.find(target);
cout << "c.find(),milli-seconds:" << (clock() - timeStart) << endl;
if (pItem!=c.end())
{
//注意这里取(*pItem).second表示取value
cout << "found:" << (*pItem).second << endl;
}
else
{
cout << "not found!" << endl;
}
}
}
#include<unordered_set>
namespace jj09
{
//unordered_set数据结构为哈希表
using namespace std;
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());
//注意这里的插入方法,是不允许以下标的方式插入数据的
c.insert(string(buf));
}
catch (const std::exception& p)
{
cout << "i:" << i << " " << p.what();
abort();
}
}
cout << "milli-seconds:" << (clock() - timeStart) << endl;
cout << "unordered_set.size()" << c.size() << endl;
cout << "unordered_set.max_size()" << c.max_size() << endl;
//输出篮子的个数
cout << "unordered_set.bucker_count()" << c.bucket_count() << endl;
//输出填充因子
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";
}
}
}
#include<map>
namespace jj10
{
using namespace std;
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 (const std::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;
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;
}
}
}
#include<set>
namespace jj11
{
using namespace std;
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 (const std::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;
string target = get_a_target_string();
{
timeStart = clock();
auto pItem = find(c.begin(), c.end(), target);
if (pItem!=c.end())
{
cout << "found," << *pItem << endl;
}
else
{
cout << "not found!" << endl;
}
}
{
timeStart = clock();
auto pItem = c.find(target);
cout << "c.find(),milli-seconds:" << (clock() - timeStart) << endl;
if (pItem!=c.end())
{
cout << "found," << *pItem << endl;
}
else
{
cout << "not found!" << endl;
}
}
}
}
#include<map>
namespace jj12
{
using namespace std;
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());
c.insert(pair<long, string>(i, buf));
}
catch (const std::exception& p)
{
cout << "i:" << i << " " << p.what() << endl;
abort();
}
}
cout << "milli-seconds:" << (clock() - timeStart) << endl;
cout << "multimap.size():" << c.size() << endl;
cout << "multimap.maxsize():" << c.max_size() << endl;
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:" << (*pItem).second << endl; //因为这是一个pair，第一个参数是key，第二个参数是value
}
else
{
cout << "not found!" << endl;
}
}
}
namespace jj13
{
using namespace std;
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 (const std::exception& p)
{
cout << "i:" << i << " " << p.what();
abort();
}
}
cout << "milli-second:" << (clock() - timeStart) << endl;
cout << "unordered_multiset.size()" << c.size() << endl;
cout << "unordered_multiset.max_size()" << c.max_size() << endl;
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.bucket_count()" << c.max_bucket_count() << endl;
for (unsigned i = 0; i < 20; i++)
{
cout << "bucket #" << i << " has " << c.bucket_size(i) << " elements \n";
}
}
}
namespace jj14
{
using namespace std;
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 (const std::exception& p)
{
cout << "i:" << i << " " << p.what() << endl;
abort();
}
}
cout << "mili-seconds:" << (clock() - timeStart) << endl;
cout << "set.size():" << c.size() << endl;
cout << "set.max_size():" << c.max_size() << endl;
string target = get_a_target_string();
{
auto pItem = find(c.begin(), c.end(), target);
cout << "::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);
cout << "c.find(),milli-seconds:" << (clock() - timeStart) << endl;
if (pItem != c.end())
{
cout << "found:" << *pItem << endl;
}
else
{
cout << "not found!" << endl;
}
}
}
}
namespace jj15
{
using namespace std;
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[]进行insertion
c.insert(pair<long, string>(i, buf));
}
catch (const std::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;
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).first << endl;
}
else
{
cout << "not found!" << endl;
}
}
}
int main()
{
long value;
int select=0;
cout << "please enter a select to test: 0 to quit: ";
//cout << "select:";
cin >> select;
while (select!=0)
{
if (select!=1)
{
cout << "how many elements:";
cin >> value;
}
switch (select)
{
case 1:
jj01::test_array();
break;
case 2:
jj02::test_vector(value);
break;
case 3:
jj03::test_list(value);
break;
case 4:
jj04::test_forward_list(value);
break;
case 5:
jj05::test_deque(value);
break;
case 6:
jj06::test_stack(value);
break;
case 7:
jj07::test_queue(value);
break;
case 8:
jj08::test_unordered_map(value);
break;
case 9:
jj09::test_unordered_set(value);
break;
case 10:
jj10::test_map(value);
break;
case 11:
jj11::test_multiset(value);
break;
case 12:
jj12::test_multimap(value);
break;
case 13:
jj13::test_unordered_multiset(value);
break;
case 14:
jj14::test_set(value);
break;
case 15:
jj15::test_unordered_multimap(value);
break;
default:
break;
}
cout << "\nanother test? (0 to quit): ";
cin >> select;
}
system("pause");
return 0;
}