C++ STL源码剖析之容器配接器stack与queue、priority_queue

下面本节带着这个问题来深入源码分析。

在stack的源码中我们关注两点：- 默认为deque- 内部函数实现是调用_Sequence对应容器的函数。

int test_stack() {
    cout<<"============test_stack============="<<endl;
    clock_t timeStart = clock();
    stack<int, list<int>> c;
    for (long i = 0; i < 100000; i++)
        c.push(i+1);
    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;
    cout << "use stack milli-seconds : " << (clock() - timeStart) << endl;
    timeStart=clock();
    stack<int, deque<int>> c1;
    for (long i = 0; i < 100000; i++)
        c1.push(i+1);
    cout << "stack.size()= " << c1.size() << endl;
    cout << "stack.top()= " << c1.top() << endl;
    c1.pop();
    cout << "stack.size()= " << c1.size() << endl;
    cout << "stack.top()= " << c1.top() << endl;
    cout << "use stack milli-seconds : " << (clock() - timeStart) << endl;
    // vector可以作为stack的底层容器
    stack<int, vector<int>> c2;
    for (long i = 0; i < 100000; i++)
        c2.push(i+1);
    cout << "stack.size()= " << c2.size() << endl;
    cout << "stack.size()= " << c2.size() << endl;
    cout << "stack.top()= " << c2.top() << endl;
    cout << "use stack milli-seconds : " << (clock() - timeStart) << endl;
}

在queue的源码中我们关注两点：- 默认_Sequence为deque- 内部函数实现是调用_Sequence对应容器的函数。

其对应的UML类图如下：

同理，优先队列则是使用vector作为默认容器。

template<typename _Tp, typename _Sequence = vector<_Tp>,
typename _Compare  = less<typename _Sequence::value_type> >
class priority_queue
{
public:
    typedef typename _Sequence::value_type                value_type;
    typedef typename _Sequence::reference                 reference;
    typedef typename _Sequence::const_reference           const_reference;
    typedef typename _Sequence::size_type                 size_type;
    typedef          _Sequence                            container_type;
protected:
    //  See queue::c for notes on these names.
    _Sequence  c;
    _Compare   comp;
public:
    reference
    top() 
    {
        __glibcxx_requires_nonempty();
        return c.front();
    }
    void
    push(const value_type& __x)
        c.push_back(__x);
    }
}

测试这两个容器配接器支持的底层容器：

对于queue底层容器可以是deque，也可以是list，但不能是vector,map,set，使用默认的deque效率在插入方面比其他容器作为底层要快！

int test_priority_queue() {
    cout<<"============test_priority_queue============="<<endl;
    clock_t timeStart = clock();
    priority_queue<int, deque<int>> c1;
    for (long i = 0; i < 100000; i++) {
        c1.push(i+1);
    }
    cout << "stack.size()= " << c1.size() << endl;
    cout << "stack.top()= " << c1.top() << endl;
    c1.pop();
    cout << "stack.size()= " << c1.size() << endl;
    cout << "stack.top()= " << c1.top() << endl;
    cout << "use deque milli-seconds : " << (clock() - timeStart) << endl;
    priority_queue<int, vector<int>> c2;
    for (long i = 0; i < 100000; i++)
        c2.push(i+1);
    cout << "stack.size()= " << c2.size() << endl;
    cout << "stack.top()= " << c2.top() << endl;
    c2.pop();
    cout << "stack.size()= " << c2.size() << endl;
    cout << "stack.top()= " << c2.top() << endl;
    cout << "use stack milli-seconds : " << (clock() - timeStart) << endl;

因此，stack、queue、priority_queue不被称为容器， 把它称为容器配接器。