c++ STL stack用法

 stacks are implemented as containers adaptors, which are classes that use an encapsulated object of a specific container class as its underlying container, providing a specific set of member functions to access its elements. Elements are pushed/popped from the "back" of the specific container, which is known as the top of the stack.
c++中stack是建立在底层容器基础上的。
The underlying container may be any of the standard container class templates or some other specifically designed container class. The only requirement is that it supports the following operations:

back()// access the last elment
push_back()
pop_back()

实现C++  STL，栈有两个参数。

template < class T, class Container = deque<T> > class stack;

参数示意：

• T: 元素类型
• Container: 被用于存储和访问元素的的类型
• Therefore, the standard container class templates vector, deque and list can be used. By default, if no container class is specified for a particular stack class, the standard container class template deque is used.
• 如果不指定第2个参数（容器类型，就为deque)

构造函数 

    explicit stack ( const Container& ctnr = Container() );

Constructs a stack container adaptor object.
A container adaptor keeps a container object as data. This container object is a copy of the argument passed to the constructor, if any, otherwise it is an empty container.

// constructing stacks
#include <iostream>
#include <vector>
#include <deque>
#include <stack>
using namespace std;

int main ()
{
  deque<int> mydeque (3,100);     // deque with 3 elements
  vector<int> myvector (2,200);   // vector with 2 elements

  stack<int> first;               // empty stack
  stack<int> second (mydeque);    // stack initialized to copy of deque

  stack<int,vector<int> > third;  // empty stack using vector
  stack<int,vector<int> > fourth (myvector);

  cout << "size of first: " << (int) first.size() << endl;
  cout << "size of second: " << (int) second.size() << endl;
  cout << "size of third: " << (int) third.size() << endl;
  cout << "size of fourth: " << (int) fourth.size() << endl;

  return 0;
}

注意，当容器类型不是默认的deque时，一定要指定容器类型，否则报错。

基本操作：

void push ( const T& x );

void pop ( );

 移去顶元素，The value of this element can be retrieved before being popped by calling member stack::top.

// stack::push/pop
#include <iostream>
#include <stack>
using namespace std;

int main ()
{
  stack<int> mystack;

  for (int i=0; i<5; ++i) mystack.push(i);

  cout << "Popping out elements...";
  while (!mystack.empty())
  {
     cout << " " << mystack.top();
     mystack.pop();
  }
  cout << endl;

  return 0;
}

输出： 4,3 ，2,1,0

  value_type& top ( );
const value_type& top ( ) const;
 Returns a reference to the next element in the stack. Since stacks are last-in first-out containers this is also the last element pushed into the stack.

// stack::top
#include <iostream>
#include <stack>
using namespace std;

int main ()
{
  stack<int> mystack;

  mystack.push(10);
  mystack.push(20);

  mystack.top() -= 5;

  cout << "mystack.top() is now " << mystack.top() << endl;

  return 0;
}

输出：mystack.top() is now 15

bool empty ( ) const; 检测是否为空。