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📜  用于自平衡 BST 的Python库

📅  最后修改于: 2022-05-13 01:55:43.351000             🧑  作者: Mango

用于自平衡 BST 的Python库

在这里，我们将看到在Python上模拟Java中可用的库框架 TreeSet。在某些情况下会出现不允许重复条目的情况，尤其是在对象由其唯一性唯一标识的任何管理软件中。在这篇文章中，让我们看看如何以 Python 的方式做到这一点。

在我们的实现中，“TreeSet”类是一个类似于Java TreeSet 的二叉树集合。 TreeSet 将在添加/删除元素时自动排序。不会添加重复的元素。

已包含的功能有：

  • 将元素插入 TreeSet。
  • 将多个元素插入 TreeSet。
  • 从 TreeSet 中获取 ceil 值。
  • 从 TreeSet 中获取楼层值。
  • 从 TreeSet 中删除一个元素。
  • 从 TreeSet 中删除所有元素。
  • 获取 TreeSet 的浅表副本。
  • 从 TreeSet 中弹出一个元素。
Python3
# The bisect module ensures the automatic sort after insertion
import bisect
   
class TreeSet(object):
    """
    Binary-tree set like java Treeset.
    Duplicate elements will not be added.
    When added new element, TreeSet will be
    sorted automatically.
    """
    def __init__(self, elements):
        self._treeset = []
        self.addAllElements(elements)
   
    # To add many elements
    def addAllElements(self, elements):
        for element in elements:
            if element in self: continue
            self.addElement(element)
   
    # To add an element
    def addElement(self, element):
        if element not in self:
            bisect.insort(self._treeset, element)
   
    # To get ceiling value
    def ceiling(self, e):
        index = bisect.bisect_right(self._treeset, e)
        if self[index - 1] == e:
            return e
        return self._treeset[bisect.bisect_right(self._treeset, e)]
   
    def floor(self, e):
        index = bisect.bisect_left(self._treeset, e)
        if self[index] == e:
            return e
        else:
            return self._treeset[bisect.bisect_left(self._treeset, e) - 1]
   
    def __getitem__(self, num):
        return self._treeset[num]
   
    def __len__(self):
        return len(self._treeset)
   
    def clearElements(self):
        """
        Delete all elements in TreeSet.
        """
        self._treeset = []
   
    def clone(self):
        """
        Return shallow copy of self.
        """
        return TreeSet(self._treeset)
   
    def removeElement(self, element):
        """
        Remove element if element in TreeSet.
        """
        try:
            self._treeset.remove(element)
        except ValueError:
            return False
        return True
   
    def __iter__(self):
        """
        Do ascending iteration for TreeSet
        """
        for element in self._treeset:
            yield element
   
    def pop(self, index):
        return self._treeset.pop(index)
   
    def __str__(self):
        return str(self._treeset)
   
    def __eq__(self, target):
        if isinstance(target, TreeSet):
            return self._treeset == target.treeset
        elif isinstance(target, list):
            return self._treeset == target
   
    def __contains__(self, e):
        """
        Fast attribution judgement by bisect
        """
        try:
            return e == self._treeset[bisect.bisect_left(self._treeset, e)]
        except:
            return False
  
if __name__ == '__main__':
    treeSet = TreeSet([3, 7, 7, 1, 3, 10])
   
    # As there is no 5, floor of this gives the 
    # next least value  in the treeset i.e. 3 
    print("treeSet.floor(5) : ", treeSet.floor(5)) 
      
    # As there is no 4, ceil of this gives the 
    # next highest value in the treeset i.e. 7
    print("treeSet.ceiling(4) : ", treeSet.ceiling(4)) 
  
    # As there is no 2, floor of this gives the next
    # least value  in the treeset i.e. 1
    print("treeSet.floor(2) : ", treeSet.floor(2)) 
  
    # As there is 3, ceil will give 3 as it is 
    print("treeSet.ceiling(3) : ", treeSet.ceiling(3))  
      
    # As there is 10, floor will give 10 as it is
    print("treeSet.floor(10) : ", treeSet.floor(10))  
      
    # No duplicates printed
    print("treeSet : ", treeSet) 
   
    # 2nd example
    treeSet = TreeSet([30, 70, 20, 70, 10, 30])
      
    # No duplicates printed
    print("2nd example treeSet :", treeSet) 
      
    treeSet.addElement(40)
    print("Adding 40 to the above, it is arranged in\
    sorted order : ", treeSet) 
       
    treeSet.removeElement(70)
    print("After removing 70 ", treeSet)
       
    treeSet.removeElement(50)
    print("After removing 50, no issue even if not\
    available ", treeSet)  
    # There is no 50 available
       
    treeSet.addAllElements([30, 40, 50, 60])
    print("After adding many elements, duplicate are\
    not taken :", treeSet)
       
    # Getting first element of treeset
    print(treeSet[0])
       
    # See, how elements can be retrieved
    print(treeSet[-1], treeSet[5], treeSet[-2], 
          treeSet[-3], treeSet[-4], treeSet[-5])
       
    # Check for the existence of 10 and since
    # found, it returns true
    print(10 in treeSet)
       
    # Check for the existence of 100 and since 
    # not found, it returns false
    print(100 in treeSet)
   
    for i in TreeSet([10, 30, 40]):
        print(i)


输出 ：