我有下面的程序来实现一个分类包。它添加了元素 在给出列表时成功地按排序(升序)排序。 当我用另一个包的参数创建一个新的已排序包时,它不是按排序顺序(而是按降序排列)。见下文
谢谢你的帮助
# Array Class
#----------------------------------------------------
class Array(object): # Represents an array.
DEFAULT_CAPACITY = 5
def __init__ (self, capacity, fillValue = None):
'''Capacity = static size of array. fillValue is placed at each element'''
self._items = list()
self._capacity = capacity
self._logicalSize = 0
self._fillValue = fillValue
for count in range(capacity):
self._items.append(fillValue)
def __getitem__(self, index): return self._items[index]
def __setitem__(self, index, newItem):
self._items[index] = newItem
# ArraySortedBag Class
#----------------------------------------------------
class ArraySortedBag(object):
'''An array-based bag implementation'''
def __init__(self, sourceCollection = None):
'''Sets the initial state of self, which includes the contents
of sourceCollection, if it's present'''
self._items = Array(10)
self._size = 0
if sourceCollection:
for item in sourceCollection:
self.add(item)
def __len__(self): return self._size
def __iter__(self):
cursor = 0
while cursor < len(self):
yield self._items[cursor]
cursor += 1
def add(self, item):
'''Adds item to self.'''
insertIndex = 0
# First found the index where the item will be inserted at
for i in range(self._size):
if self._items[i] > item:
insertIndex = i
break
# Then, shift items down by one position until the insertIndex,
for i in range (self._size, insertIndex, -1):
self._items[i] = self._items[i-1]
# Last, assign value to _items[insertIndex]
self._items[insertIndex] = item
self._size += 1
# Test Driver
#----------------------------------------------------
if __name__ == "__main__":
b1 = ArraySortedBag([2000, 2, 1000])
print ("Display bag b1")
for i in b1: # <------ Correct order, ascending order
print (i)
b2 = ArraySortedBag(b1)
print ("\nDisplay bag b2")
for i in b2: # <----- Wrong order, descending order
print (i)
为了将项添加到已排序的列表中,以便维护列表的排序,我建议使用bisect library'sinsort_left或insort_right。在
在ArraySortedBag类的第二个实例化中,传递的是一个已排序的列表。ArraySortedBag.init()方法使用add()方法添加项。调用add()时,要添加的项永远不会少于现有列表。因此,insertIndex仍然等于零。因此,新项被添加到列表的开头。在
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