尝试使用数组构建堆栈算法

Question

我正在尝试这样做，但它总是错误的。我不明白我应该怎么做...这是我的代码：

class WrongStack:
def __init__(self):        
    self.__items = numpy.array([])

def push(self, item): 
    numpy.concatenate(self.__items,item)

def pop(self):  
    return numpy.delete(self.__items,0,-1)

def peek(self):  
    return self.__items[len(self.__list) - 1]

def is_empty(self):            
    return len(self.__items) == 0

def size(self):                 
    return len(self.__items)


s = WrongStack()
number = input('Choose a number, 0 to finish')
while number != '0':
  s.push(numpy.array([nmr]))
  number = input('Choose a number, 0 to finish')
while not s.is_empty():
  number = s.pop()
  print(number)

错误是：

File "C:/Users/JJ/OneDrive - ISCTE-IUL/EDA/Aula 4.py", line 55, in <module>
s.push(numpy.array([nmr]))

File "C:/Users/JJ/OneDrive - ISCTE-IUL/EDA/Aula 4.py", line 38, in push
numpy.concatenate(self.__items,item)

File "<__array_function__ internals>", line 6, in concatenate
TypeError: only integer scalar arrays can be converted to a scalar index

我知道这不是构建普通堆栈的方法，但我必须这样做。

Answer 1

对您的代码进行修改以使其正常工作。

在我更改代码的地方放置了“Mod”。

代码

import numpy as np

class WrongStack:
  def __init__(self):        
      self.__items = np.array([])

  def push(self, item): 
      # Mod--concatenate takes list contains items to concatenate
      self.__items = np.concatenate([self.__items,item])

  def pop(self):  
      # Mod--np.delete returns a new array
            # also retrieve last element before delete
      last = self.__items[-1]
      self.__items = np.delete(self.__items,-1, 0)
      return last

  def peek(self):  
      return self.__items[len(self.__list) - 1]

  def is_empty(self): 
      # Mod--use function size    
      return self.size() == 0

  def size(self):                 
      return len(self.__items)

  def __str__(self):
    # Mod--added for display the array
    return str(self.__items)

s = WrongStack()
number = input('Choose a number, 0 to finish: ')
while len(number) > 0 and number != '0': #Mod done if no input or '0' entered
  # Mod--convert numer to integer
  s.push(np.array([number], dtype=np.int32)) # specify type (i.e. int32)
  number = input('Choose a number, 0 to finish: ')

# Mod--print array created
print('Array created:', s)

while not s.is_empty():
  number = s.pop()
  print('number: ', number)

测试

Choose a number, 0 to finish: 1
Choose a number, 0 to finish: 2
Choose a number, 0 to finish: 3
Choose a number, 0 to finish: 4
Choose a number, 0 to finish: 5
Choose a number, 0 to finish: 0
Array created: [1. 2. 3. 4. 5.]
number:  5.0
number:  4.0
number:  3.0
number:  2.0
number:  1.0

替代方案

依赖于 Numpy 固定大小的数组。使用切片和范围检查来确保我们保持在分配的大小范围内。

import numpy as np

class WrongStack:
  def __init__(self, maxlen=100):        
      self.__items = np.array([0]*maxlen) # Fixed size Numpy array
      self._count = 0
      self._maxlen = maxlen

  def push(self, item): 
      # Mod--concatenate takes list contains items to concatenate
      if self._count < self._maxlen:
        self.__items[self._count] = item
        self._count += 1
      else:
        print('push: no more space')


  def pop(self):  
      # Mod--np.delete returns a new array
            # also retrieve last element before delete
      if self._count > 0:
        last = self.__items[self._count-1]
        self._count -= 1
        return last
      else:
        return None

  def peek(self):
      if self._count > 0:
        return self.__items[self._count-1]
      else:
        return None

  def is_empty(self): 
      # Mod--use function size    
      return self.size() == 0

  def size(self):                 
      return self._count

  def __str__(self):
    # Mod--added for display the array
    return str(self.__items[:self._count])

s = WrongStack(10) # will handle stack with up to 10 elements
number = input('Choose a number, 0 to finish: ')
while len(number) > 0 and number != '0': #Mod done if no input or '0' entered
  # Mod--convert numer to integer
  s.push(number) # specify type (i.e. int32)
  number = input('Choose a number, 0 to finish: ')

# Mod--print array created
print('Array created:', s)

while not s.is_empty():
  number = s.pop()
  print('number: ', number)

Answer 2

您正在尝试将 numpy 数组用作堆栈，这可能不会像您希望的那样工作。 Numpy 数组是为数学计算而设计的，而不是作为通用数据结构。

而只是使用 Python 列表来实现您的堆栈。事实上，Python 文档甚至包括 a section 来说明如何做到这一点：

>>> stack = [3, 4, 5]
>>> stack.append(6)
>>> stack.append(7)
>>> stack
[3, 4, 5, 6, 7]
>>> stack.pop()
7
>>> stack
[3, 4, 5, 6]
>>> stack.pop()
6
>>> stack.pop()
5
>>> stack
[3, 4]