生成、遍历和打印二叉树

Question

I generated perfectly balanced binary tree and I want to print it. In the output there are only 0s instead of the data I generated. I think it's because of the line in function printtree that says print(tree.elem) , cause in the class self.elem = 0 .

How can I connect these two functions generate and printtree ?

class BinTree:

    def __init__(self):
        self.elem = 0
        self.left = None
        self.right = None


def generate(pbt, N):
    if N == 0:
        pbt = None
    else:
        pbt = BinTree()
        x = input()
        pbt.elem = int(x)
        generate(pbt.left, N // 2)
        generate(pbt.right, N - N // 2 - 1)

def printtree(tree, h):
    if tree is not None:
        tree = BinTree()
        printtree(tree.right, h+1)
        for i in range(1, h):
            print(end = "......")
            print(tree.elem)
            printtree(tree.left, h+1)

Hope somebody can help me. I am a beginner in coding.

For example: N=6, pbt=pbt, tree=pbt, h=0

input:

1
2
3
4
5
6

and the output:

......5 
............6 
1 
............4 
......2 
............3

Answer 1

I'd suggest reading up on: https://www.geeksforgeeks.org/tree-traversals-inorder-preorder-and-postorder/

Basically, there are three ways to traverse a binary tree; in-order, post-order and pre-order.

The issue with your print statement is that, you're reassigning the tree that is being passed in, to an empty tree.

  if tree is not None:
        tree = BinTree()

Right? If tree is not none and has something, lets reassign that to an empty tree.

Traversing a tree is actually a lot more simpler than you'd imagine. I think the complexity comes in just trying to imagine in your head how it all works out, but the truth is that traversing a tree can be done in 3 - 4 lines.