stack
Stacks are a type of container adaptor, specifically designed to operate in a LIFO context (last-in first-out), where elements are inserted and extracted only from one end of the container.
stacks are implemented as container 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.
The underlying container may be any of the standard container class templates or some other specifically designed container class. The container shall support the following operations:
- empty
- size
- back
- push_back
- pop_back
stack 是一种先进后出（First In Last Out, FILO）的数据结构，它只有一个出口。
stack 容器允许新增元素、移除元素、取得栈顶元素，但是除了最顶端外，没有任何其他方法可以存取stack的其他元素。
换言之，stack不允许有遍历行为。
stack 没有迭代器 : 不允许遍历行为，自然也就不提供迭代器了。
| member function | definition |
|---|---|
| (constructor) | Construct stack |
| empty | Test whether container is empty |
| size | Return size |
| top | Access next element |
| push | Insert element |
| emplace | Construct and insert element |
| pop | Remove top element |
| swap | Swap contents |
构造函数
赋值
stack<T> stkT; // 默认构造函数，stack采用模版类实现
stack(const stack& stk); // 拷贝构造函数
stack& operator=(const stack& stk); // 重载赋值操作符
数据存取
void push(T elem); // 向栈顶添加元素
void pop(); // 从栈顶移除第一个元素
T& top(); // 返回栈顶元素
大小
bool empty(); // 判断堆栈是否为空
int size(); // 返回栈的大小