STL序列式容器之stack

stack是一种先进先出（First In Last Out， FILO）的数据结构。它只有一个出口。stack允许新增元素、移除元素、取得最顶端元素。它只有一个出口；stack允许新增元素、移除元素、取得最顶端元素。单除了最顶端外，没有任何其它方法可以存取stack的其它元素。换言之，stack不许与有遍历行为。

根据stack的性质，可知stack可用之前介绍的vector，list，deque做为底层的实现进行处理；

stack的定义如下

template<class T, class Sequence = deque<T>>
class stack {friend bool operator == __STL_NULL_TMPL_ARGS(const stack&, const stack&);friend bool operator < __STL_NULL_TMPL_ARGS(const stack&, const stack&);
public: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;
public:bool empty() const {return c.empty();}size_type size() const {return c.size();}reference top() {return c.back();}const_reference top() const {return c.back();}void push(const value_type&x) {c.push_back(x);}void pop() {c.pop_back();}
};template <class T, class Sequence>
bool operator == (const stack<T, Sequence>& x, const stack<T,Sequence>&y) {return x.c == y.c;
}template <class T, class Sequence>
bool operator <  (const stack<T, Sequence>& x, const stack<T,Sequence>&y) {return x.c <  y.c;
}

从以上定义可知，只需要实现了empty(),size(),back(),push_back(),pop_back()及operator ==及<的容器都可作为stack的容器；

如需将stack的底层容器换成list；只需定义时增加Sequence参数即可