遍历数组并在索引处插入元素

Question

我必须在 python 中实现 Vector ADT。所有其他方法都有效，但我坚持执行插入和删除。

insert(index, element)：将给定元素插入到位置 index 的向量中。给定位置处和之后的元素向下移动以为新项目腾出空间。索引必须在有效范围内且向量不能满。如果 index 超出向量末尾的位置，则将该项附加到向量上。

remove(index)：从向量中移除位于 index 位置的元素。移除的元素被返回。被移除元素之后的所有元素都向下移动一个位置，以缩小因被移除元素而产生的间隙。

我的代码：

from ezarrays import Array

class Vector :
   # Creates an empty vector instance.

def __init__(self) :

   self._theArray = Array( 2 )
   self._capacity = 2
   self._numItems = 0

   # Returns the number of elements in the vector.
def __len__(self):
   return self._numItems

   # Returns the element at the given index position.

def __getitem__(self, index) :
    assert index >= 0 and index < self._numItems, "Index out of range."
    return self._theArray[index]

   # Stores the given element at the given index position. 
  def __setitem__(self, index, element) :
     assert index >= 0 and index <= self._numItems, "Index out of range."
     if index == self._numItems :
       self.append(element)
    else :
      self._theArray[index] = element

   # Returns a string representation of the vector in the form: [e1, e2 ...]
  def __repr__(self) :
    if self._numItems == 0 :
      return "[]"
    else :
      result = ""
      i = 0
      while i < self._numItems - 1 :
        result = result + str(self._theArray[i]) + ", "
        i = i + 1

      result = result + str(self._theArray[i])
      return "[" + result + "]"

   # Appends the given element to the end of the vector.
  def append(self, element) :
    if self._numItems == self._capacity :
       self._expandArray()
    index = self._numItems
    self._theArray[index] = element
    self._numItems = self._numItems + 1

  # Returns a Boolean indicating if the given element is in the vector.
  def __contains__(self, element) :
    for i in range(self._numItems):
      if self._theArray[i] == element:
        return True
    return False

   # Returns the position index within the vector that contains the given element
   def index(self, element) :
     assert element in self, "The element must be in the list."
     for i in range(self._numItems) :
       index = self._theArray[i]
       if index == element :
        return i

  # Inserts the given element into the vector at position index     
   def insert(self, index, element) :
     assert index >= 0 and index <= self._numItems, "Index out of range."
     if self._numItems == self._capacity:
       self._expandArray()
     i=0
     while i < len(self._theArray):
         element = self._theArray[i] 
        do_action(element)
        if check(element):
             del self.-_theArray[i]
        else:
            i+=1    

  # Removes the element at position index from the vector. 
  def remove(self, index) :
    pass

  # Removes all elements from the vector resulting in an empty vector   
   def clear(self) :
     self.theArray = Array(2)
     self._capacity = 2
     self._numItems = 0

  # expands the array by expanding capacity and making a new array
  def _expandArray(self) :
    newCapacity = self._capacity * 2
    newArray = Array( newCapacity )
    for i in range (len(self._theArray)):
      newArray[i] = self._theArray[i]
    self._theArray = newArray

ezarrays的实现（也就是数组） 导入 ctypes

class Array :
   # Creates an array with size elements.
  def __init__( self, size ):               
    assert size > 0, "Array size must be > 0"
    self._size = size    

     # Create the array structure using the ctypes module.
    PyArrayType = ctypes.py_object * size          
    self._elements = PyArrayType()

     # Initialize each element.
    self.clear(None)                        

   # Returns the size of the array.
  def __len__( self ):
    return self._size

   # Gets the contents of the index element.
  def __getitem__( self, index ):                  
    assert index >= 0 and index < len(self), "Array subscript out of range"
    return self._elements[ index ]

   # Puts the value in the array element at index position.
  def __setitem__( self, index, value ):
    assert index >= 0 and index < len(self), "Array subscript out of range"
    self._elements[ index ] = value                 

   # Clears the array by setting each element to the given value.
   def clear( self, value ) :
    for i in range(len(self)) :
      self._elements[i] = value


# Implementation of the Array2D ADT using an array of arrays. 
class Array2D :  
   # Creates a 2-D array of size numRows x numCols.
  def __init__( self, numRows, numCols ):
     # Create a 1-D array to store an array reference for each row.
    self._theRows = Array(numRows)

     # Create the 1-D arrays for each row of the 2-D array.
    for i in range( numRows ) :
      self._theRows[i] = Array(numCols)

   # Returns the number of rows in the 2-d array.
  def numRows( self ):
    return len( self._theRows )

   # Returns the number of columns in the 2-d array.
  def numCols( self ):
    return len( self._theRows[0] )

   # Clears the array by setting every element to the given value.
  def clear( self, value ):
    for row in range(len(self._theRows)) :
      self._theRows[row].clear(value)

   # Get the contents of the element at position [i, j]
  def __getitem__( self, ndxTuple ):                                
    assert len(ndxTuple) == 2, "Invalid number of array subscripts." 
    row = ndxTuple[0]
    col = ndxTuple[1]
    assert row >= 0 and row < self.numRows() \
       and col >= 0 and col < self.numCols(), \
           "Array subscript out of range."
    the1dArray = self._theRows[row]
    return the1dArray[col]                       

   # Set the contents of the element at position [i,j] to value.
  def __setitem__( self, ndxTuple, value ):
     assert len(ndxTuple) == 2, "Invalid number of array subscripts."    
     row = ndxTuple[0]
     col = ndxTuple[1]
     assert row >= 0 and row < self.numRows() \
       and col >= 0 and col < self.numCols(), \
           "Array subscript out of range."
    the1dArray = self._theRows[row]
    the1dArray[col] = value  

Answer 1

好的，因为我没有您正在使用的模块，我无法真正测试代码，但这是我的想法：

def remove(self, idx):
    elem = self._theArray[idx]
    new_array = Array(self._capacity-1)

    for i in range(0, self._numItems):
        if i != idx:
            new_array.append(self._theArray[i])

    self._theArray = new_array
    return elem

def insert(self, index, element) :
    assert index >= 0 and index <= self._numItems, "Index out of range."
    if self._numItems == self._capacity:
        self._expandArray()

    for i in reversed(range(index, self._numItems)):
        self._theArray[i+1] = self._theArray[i]

    self._theArray[index] = element