找到二叉树中第n个节点的Python程序

当需要使用二叉树的中序遍历找到第n个节点时，创建一个二叉树类并定义方法来设置根元素，添加左/右元素，执行中序遍历等操作。创建该类的实例，即可使用其方法。

以下是该方法的演示 –

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例子

class BinaryTree_struct:
   def __init__(self, key=None):
      self.key = key
      self.left = None
      self.right = None

   def set_root(self, key):
      self.key = key

   def inorder_nth(self, n):
      return self.inorder_nth_helper_fun(n, [])

   def inorder_nth_helper_fun(self, n, in_ord):
      if self.left is not None:
         temp = self.left.inorder_nth_helper_fun(n, in_ord)
         if temp is not None:
            return temp
      in_ord.append(self)
      if n == len(in_ord):
         return self
      if self.right is not None:
         temp = self.right.inorder_nth_helper_fun(n, in_ord)
         if temp is not None:
            return temp

   def insert_t0_left(self, new_node):
      self.left = new_node

   def insert_to_right(self, new_node):
      self.right = new_node

   def search_elem(self, key):
      if self.key == key:
         return self
      if self.left is not None:
         temp = self.left.search_elem(key)
         if temp is not None:
            return temp
      if self.right is not None:
         temp = self.right.search_elem(key)
         return temp
      return None

btree_instance = None

print('Menu (this assumes no duplicate keys)')
print('insert <data> at root')
print('insert <data> left of <data>')
print('insert <data> right of <data>')
print('inorder ')
print('quit')

while True:
   do = input('What would you like to do? ').split()

   operation = do[0].strip().lower()
   if operation == 'insert':
      data = int(do[1])
      new_node = BinaryTree_struct(data)
      suboperation = do[2].strip().lower()
      if suboperation == 'at':
         btree_instance = new_node
      else:
         position = do[4].strip().lower()
         key = int(position)
         ref_node = None
         if btree_instance is not None:
            ref_node = btree_instance.search_elem(key)
         if ref_node is None:
            print('No such key.')
            continue
         if suboperation == 'left':
            ref_node.insert_t0_left(new_node)
         elif suboperation == 'right':
            ref_node.insert_to_right(new_node)

   elif operation == 'inorder':
      if btree_instance is not None:
         index = int(do[1].strip().lower())
         node = btree_instance.inorder_nth(index)
         if node is not None:
            print('中序遍历的第n项: {}'.format(node.key))
         else:
            print('索引超出可能的最大值。')
      else:
         print('二叉树为空...')

   elif operation == 'quit':
      break

输出

Menu (this assumes no duplicate keys)
insert <data> at root
insert <data> left of <data>>
insert <data> right of <data>
inorder
quit
What would you like to do? insert 5 at root
What would you like to do? insert 6 left of 5
What would you like to do? insert 8 right of 5
What would you like to do? inorder 5
索引超出可能的最大值。
What would you like to do? 6
6