源代码来自sgi-2.91版本stl_queue.h
queue总述
先了解deque容器->deque
(1)因为deque容器双向push和pop的特性,所以queue的底层实现可以完全由deque代替,所以queue与其叫容器,不如叫deque的适配器。
(2)不带iterator,不能遍历
(3)底层实现不一定要deque,list也可以,因为双向链表满足头部push、pop特性
queue类
#ifndef __STL_LIMITED_DEFAULT_TEMPLATES
template <class T, class Sequence = deque<T> > //默认底层由deque实现
#else
template <class T, class Sequence> //也可以换其他容器实现
#endif
class queue {
friend bool operator== __STL_NULL_TMPL_ARGS (const queue& x, const queue& y);
friend bool operator< __STL_NULL_TMPL_ARGS (const queue& x, const queue& y);
public:
/*类型定义*/
typedef typename Sequence::value_type value_type;
typedef typename Sequence::size_type size_type;
typedef typename Sequence::reference reference;
typedef typename Sequence::const_reference const_reference;
protected:
Sequence c; //创建底层deque容器
public:
/*可以发现这些操作完全调用deque实现*/
bool empty() const { return c.empty(); }
size_type size() const { return c.size(); }
reference front() { return c.front(); }
const_reference front() const { return c.front(); }
reference back() { return c.back(); }
const_reference back() const { return c.back(); }
void push(const value_type& x) { c.push_back(x); }
void pop() { c.pop_front(); }
};
运算符重载
template <class T, class Sequence>
bool operator==(const queue<T, Sequence>& x, const queue<T, Sequence>& y) {
return x.c == y.c;
}
template <class T, class Sequence>
bool operator<(const queue<T, Sequence>& x, const queue<T, Sequence>& y) {
return x.c < y.c;
}