数据结构与算法之Stack（栈）——重新实现

之前发过一篇stack的实现，是采用dart内置的List类并固定长度数组实现的。这里重新实现一版，重复利用List类内置特性和方法。实现更为简洁。

 class Stack<E> {
   final List<E> _stack;

   Stack() : _stack = <E>[];

   bool get isEmpty => _stack.isEmpty;
   bool get isNotEmpty => _stack.isNotEmpty;
   int get size => _stack.length;

   Iterable<E> get content => _stack.reversed;

   void push(E e) => _stack.add(e);

   E pop() {
     if (_stack.isEmpty) throw StackEmptyException;
     return _stack.removeLast();
   }

   E get top {
     if (_stack.isEmpty) throw StackEmptyException;
     return _stack.last;
   }
 }

 class StackEmptyException implements Exception {
   const StackEmptyException();
   String toString() => 'StackEmptyException';
 }