text: //
  //  Stack.h
  //  Stack
  //
  //  Created by sw on 2019/5/7.
  //  Copyright © 2019 WS. All rights reserved.
  //
  
  #import <Foundation/Foundation.h>
  #import "List.h"
  
  @interface Stack : NSObject<List>
  @property(nonatomic) NSUInteger size;
  @property(nonatomic) NSMutableArray *elements;
  
  + (instancetype)stack;
  @end
  