Problem:

  MathJax.Hub.Config({ tex2jax: { inlineMath: [["$","$"], ["\\(","\\)"]], processEscapes: true }});

Binary Search Tree I

 Search trees are data structures that support dynamic set operations including insert, search, delete and so on. Thus a search tree can be used both as a dictionary and as a priority queue. 

  Binary search tree is one of fundamental search trees. The keys in a binary search tree are always stored in such a way as to satisfy the following binary search tree property:

 Let $x$ be a node in a binary search tree. If $y$ is a node in the left subtree of $x$, then $y.key \leq x.key$. If $y$ is a node in the right subtree of $x$, then $x.key \leq y.key$.

  The following figure shows an example of the binary search tree.

  For example, keys of nodes which belong to the left sub-tree of the node containing 80 are less than or equal to 80, and keys of nodes which belong to the right sub-tree are more than or equal to 80. The binary search tree property allows us to print out all the keys in the tree in sorted order by an inorder tree walk.

  A binary search tree should be implemented in such a way that the binary search tree property continues to hold after modifications by insertions and deletions. A binary search tree can be represented by a linked data structure in which each node is an object. In addition to a key field and satellite data, each node contains fields left, right, and p that point to the nodes corresponding to its left child, its right child, and its parent, respectively.

  To insert a new value $v$ into a binary search tree $T$, we can use the procedure insert as shown in the following pseudo code. The insert procedure is passed a node $z$ for which $z.key = v$, $z.left = NIL$, and $z.right = NIL$. The procedure modifies $T$ and some of the fields of $z$ in such a way that $z$ is inserted into an appropriate position in the tree.

1 insert(T, z)
2     y = NIL // parent of x
3     x = 'the root of T'
4     while x &ne; NIL
5         y = x // set the parent
6         if z.key < x.key
7             x = x.left // move to the left child
8         else 
9             x = x.right // move to the right child
10    z.p = y
11
12    if y == NIL // T is empty
13        'the root of T' = z
14    else if z.key < y.key
15        y.left = z // z is the left child of y
16    else 
17        y.right = z // z is the right child of y

  Write a program which performs the following operations to a binary search tree $T$.

insert  $k$: Insert a node containing $k$ as key into $T$.

print: Print the keys of the binary search tree by inorder tree walk and  preorder tree walk respectively.

  You should use the above pseudo code to implement the insert operation. $T$ is empty at the initial state.

Input

  In the first line, the number of operations $m$ is given. In the following $m$ lines, operations represented by insert $k$ or print are given.

Output

  For each print operation, print a list of keys obtained by inorder tree walk and preorder tree walk in a line respectively. Put a space character before each key.

Constraints

The number of operations $\leq 500,000$

The number of print operations $\leq 10$.

$-2,000,000,000 \leq key \leq 2,000,000,000$

The height of the binary tree does not exceed 100 if you employ the above pseudo code.

The keys in the binary search tree are all different.

Sample Input 1

8
insert 30
insert 88
insert 12
insert 1
insert 20
insert 17
insert 25
print

Sample Output 1

 1 12 17 20 25 30 88
 30 12 1 20 17 25 88

Reference

Introduction to Algorithms, Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, and Clifford Stein. The MIT Press.



Sample input:
8
insert 30
insert 88
insert 12
insert 1
insert 20
insert 17
insert 25
print


Sample output:
 1 12 17 20 25 30 88
 30 12 1 20 17 25 88

Submission status: Memory Limit Exceeded

Solution code:
class Node(object):
    root = None

    """ ????????¨????????? """
    def __init__(self, key, parent=None, left=None, right=None):
        self.key = key
        self.parent = parent
        self.left = left
        self.right = right
        self.height = None

    @classmethod
    def insert(cls, z):
        y = None
        x = cls.root
        while x != None:
            y = x
            if z.key < x.key:
                x = x.left
            else:
                x = x.right
        z.parent = y
        if y == None:
            cls.root = z
        elif z.key < y.key:
            y.left = z
        else:
            y.right = z
        return z

    @classmethod
    def walk_preorder(cls, node):
        """ ??????????????? """
        results = []
        results.append(node.key)
        if node.left != None:
            results.append(cls.walk_preorder(node.left))
        if node.right != None:
            results.append(cls.walk_preorder(node.right))
        return results

    @classmethod
    def walk_inorder(cls, node):
        """ ??????????????? """
        results = []
        if node.left != None:
            results.append(cls.walk_inorder(node.left))
        results.append(node.key)
        if node.right != None:
            results.append(cls.walk_inorder(node.right))
        return results

    def get_type(self):
        if self.parent:
            return 'root'
        elif self.left == None and self.right == None:
            return 'leaf'
        else:
            return 'internal node'

    def get_depth(self):
        if self.parent == None:
            return 0
        else:
            depth = 1
            t = self.parent
            while t.parent != None:
                t = t.parent
                depth += 1
            return depth

    def get_height(self):
        if self.height:
            return self.height
        h_left = 0
        h_right = 0
        if self.left != None:
            h_left = self.left.get_height() + 1
        if self.right != None:
            h_right = self.right.get_height() + 1
        self.height = max(h_left, h_right)
        return self.height

    def get_degree(self):
        degree = 0
        if self.left != None:
            degree += 1
        if self.right != None:
            degree += 1
        return degree

    def get_sibling(self):
        if self.parent == None:
            return -1
        p = self.parent
        if p.left != self and p.left != None:
            return p.left
        if p.right != self and p.right != None:
            return p.right


def process_node_data(node_data):
    last = None
    for inst in node_data:
        if inst[0] == 'print':
            result = Node.walk_inorder(last.root)
            print(' {0}'.format(' '.join(map(str, flatten(result)))))
            result = Node.walk_preorder(last.root)
            print(' {0}'.format(' '.join(map(str, flatten(result)))))
        else:
            node_key = int(inst[1])
            new_node = Node(node_key)
            last = Node.insert(new_node)


def flatten(l):
    """ http://stackoverflow.com/questions/2158395/flatten-an-irregular-list-of-lists-in-python """
    import collections
    for el in l:
        if isinstance(el, collections.Iterable) and not isinstance(el, (str, bytes)):
            yield from flatten(el)
        else:
            yield el


if __name__ == '__main__':
    # ??????????????\???
    num_of_nodes = int(input())
    node_data = [input().split(' ') for _ in range(num_of_nodes)]

    # ???????????????
    # ??¨???????????????
    process_node_data(node_data)

    # ???????????????

Submission status: Accepted

Solution code:
class binaryTree:
    def __init__(self,key,p=None,l=None,r=None):
        self.key = key
        self.p = p
        self.l = l
        self.r = r

N = int(input())
treelist = [list(input().split()) for i in range(N)]
root = None

def inorder(root):
    x = root
    if x == None:
        return
    inorder(x.l)
    
    global inlist
    inlist.append(x.key)
    
    inorder(x.r)

def insert(root,z):
    y = None
    x = root
    while x != None:
        y = x
        if z.key < x.key:
            x = x.l
        else:
            x = x.r
    z.p = y

    if y == None:
        root = z
    elif z.key < y.key:
        y.l = z
    else:
        y.r = z
    return root
    
def outorder(root):
    x = root
    if x == None:
        return
    global outlist
    outlist.append(x.key)
    
    outorder(x.l)
    outorder(x.r)

for data in treelist:
    if data[0] == "insert":
        z = binaryTree(int(data[1]))
        root = insert(root,z)
        
    if data[0] == "print":
        inlist = []
        outlist = []
        
        inorder(root)
        indata = " " + " ".join([str(num) for num in inlist])
        print(indata)
 
        outorder(root)
        outdata = " " + " ".join([str(num) for num in outlist])
        print(outdata)

Submission status: Accepted

Solution code:
class Node():
    right = None
    left = None
    def __init__(self, key, parent):
        self.parent = parent
        self.key = key

class Tree():
    def __init__(self):
        self.root = None

    def insert(self, v):
        y = None
        x = self.root
        while x != None:
            y = x
            if v < x.key:
                x = x.left
            else :
                x = x.right
        z = Node(v, y)

        if y == None: # Tが空の時
            self.root = z
        elif v < y.key:
            y.left = z
        else :
            y.right = z

    # 先行
    def printPreorder(self, parent): # 最初はRootを与え再帰的に。
        print( " " + str(parent.key), end="" )
        if parent.left != None:
            self.printPreorder(parent.left)
        if parent.right != None:
            self.printPreorder(parent.right)

    # 中間
    def printInorder(self, parent): # 最初はRootを与え再帰的に。
        if parent.left != None:
            self.printInorder(parent.left)
        print( " " + str(parent.key), end="" )
        if parent.right != None:
            self.printInorder(parent.right)

def main():
    T = Tree()
    Orders =[]
    tmp =[]
    N = int( input() )
    for i in range(N):
        tmp = [input().split()]
        Orders.extend( tmp )

    for order in Orders:
        if order[0] == "insert":
            T.insert( int( order[1] ) )
        elif order[0] == "print":
            T.printInorder( T.root )
            print("")
            T.printPreorder( T.root )
            print("")

if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
# Nodeクラス


class Node:
    def __init__(self, k):
        self.k = k
        self.p = None
        self.l = None
        self.r = None

# BinarySearchクラス


class BinarySearch:
    root = None

    def insert(self, k):
        y = None
        x = self.root
        z = Node(k)
        while x:
            y = x
            if z.k < x.k:
                x = x.l
            else:
                x = x.r
        z.p = y

        if y == None:
            self.root = z
        else:
            if z.k < y.k:
                y.l = z
            else:
                y.r = z

    def preParse(self, u):
        if u == None:
            return
        print("", str(u.k), end="")
        self.preParse(u.l)
        self.preParse(u.r)

    def inParse(self, u):
        if u == None:
            return
        self.inParse(u.l)
        print("", str(u.k), end="")
        self.inParse(u.r)


if __name__ == '__main__':

    n = int(input().rstrip())
    x = BinarySearch()

    for i in range(n):
        com = input().rstrip()
        if com.startswith("insert"):
            k = int(com.split(" ")[1])
            x.insert(k)
        else:
            x.inParse(x.root)
            print()
            x.preParse(x.root)
            print()

Submission status: Accepted

Solution code:
# -*- coding: utf-8 -*-
"""
Created on Thu Jul 19 22:51:44 2018

@author: maezawa
"""

class node():
    def __init__(self, key, parent=None, right=None, left=None):
        self.key = key
        self.parent = parent
        self.right = right
        self.left = left
        
def insert(z):
    global root
    y = None
    x = root
    while x != None:
        y = x
        if z.key < x.key:
            x = x.left
        else:
            x = x.right
    z.parent = y
    
    if y == None:
        root = z
    elif z.key < y.key:
        y.left = z
    else:
        y.right = z  
    #inorder(root)
    
        
def inorder(u):
    if u == None:
        return
    inorder(u.left)
    print(' {}'.format(u.key), end = '')
    inorder(u.right)
    
def preorder(u):
    if u == None:
        return
    print(' {}'.format(u.key), end = '')
    preorder(u.left)
    preorder(u.right)
    
root = None

n = int(input())
for i in range(n):
    q = list(input().split())
    if q[0] == 'insert':
        z = node(int(q[1]))
        insert(z)
    elif q[0] == 'print':
        inorder(root)
        print()
        preorder(root)
        print()

Submission status: Accepted

Solution code:
class Node:
	def __init__(self, k):
		self.k = k
		self.l = self.r = self.p = None
	def __str__(self):
		return str(self.k)

class BST:
	def __init__(self):
		self.root = None
	
	def insert(self, node):
		p = None
		cur = self.root
		while cur != None:
			p = cur
			if node.k < cur.k:
				cur = cur.l
			else:
				cur = cur.r
		node.p = p			
		if p == None:
			self.root = node
		elif node.k < p.k:
			p.l = node
		else:
			p.r = node
	
	def print(self):
		self.print_in_order()
		self.print_pre_order()
	
	def print_in_order(self):
		st = []
		cur = self.root
		while cur != None or len(st) != 0:
			if cur != None:
				st.append(cur)
				cur = cur.l
			else:
				cur = st.pop()
				print(' ' + str(cur), end='')
				cur = cur.r
		print()
		
	def print_pre_order(self):
		st = []
		st.append(self.root)
		while len(st) != 0:
			cur = st.pop()
			print(' ' + str(cur), end='')
			if cur.r != None:
				st.append(cur.r)
			if cur.l != None:
				st.append(cur.l)
		print()

m = int(input())
bst = BST()
for i in range(m):
	cmd = list(map(str, input().split()))
	if cmd[0] == 'insert':
		bst.insert(Node(int(cmd[1])))
	else:
		bst.print()

Submission status: Accepted

Solution code:
#coding:utf-8

class MakeTree():
    def __init__(self, key, p=None, l=None, r=None):
        self.key = key
        self.p = p
        self.l = l
        self.r = r
 
def Insert(root,value):
    y = None
    x = root
    z = MakeTree(value)

    while x != None:
        y = x
        if x.key > z.key:
            x = x.l
        else:
            x = x.r
    z.p = y

    if y == None:
        root = z
    elif z.key < y.key:
        y.l = z
    else:
        y.r = z
    return root

def inParse(u):
    if u == None:
        return
    inParse(u.l)
    global inParseList
    inParseList.append(u.key)
    inParse(u.r)

def preParse(u):
    if u == None:
        return
    global preParseList
    preParseList.append(u.key)
    preParse(u.l)
    preParse(u.r)


root = None       
n = int(input())
inParseList = []
preParseList = []
for i in range(n):
    order = list(input().split())
    if order[0] == "insert":
        root = Insert(root, int(order[1]))
    else:
        inParse(root)
        preParse(root)

        print(" " + " ".join([str(i) for i in inParseList]))
        print(" " + " ".join([str(i) for i in preParseList]))
        preParseList = []
        inParseList = []

Submission status: Accepted

Solution code:
from io import StringIO
class BinaryTree:


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


    def __init__(self):
        self.root = None
        self.output = StringIO()

    def insert(self, key):
        if self.root is None:
            self.root = self.Node(key)
        else:
            root = self.root
            temp = None
            while True:
                temp = root
                if key > root.key:
                    root = root.right
                    if root is None:
                        temp.right = self.Node(key)
                        break
                else:
                    root = root.left
                    if root is None:
                        temp.left = self.Node(key)
                        break

    def ini_print_inorder(self):
        self.output = StringIO()
        self.print_inorder(self.root)
        return self.output.getvalue()

    def ini_print_preorder(self):
        self.output = StringIO()
        self.print_preorder(self.root)
        return self.output.getvalue()

    def print_inorder(self, node):
        if node is not None:
            self.print_inorder(node.left)
            print(node.key, end = " ", file = self.output)
            self.print_inorder(node.right)

    def print_preorder(self, node):
        if node is not None:
            print(node.key, end = " ", file = self.output)
            self.print_preorder(node.left)
            self.print_preorder(node.right)

    def test_insert(self, keys):
        for k in keys:
            self.insert(k)

length = int(input())
b = BinaryTree()
for _ in range(length):
    comm = input()
    if comm[0] == "i":
        com, num = comm.split(" ")
        b.insert(int(num))
    else:
        print(" ", end = "")
        print((b.ini_print_inorder())[:-1])
        print(" ", end = "")
        print(b.ini_print_preorder()[:-1])

Submission status: Accepted

Solution code:
import re

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

class BST:
  root = None
  def insert(self, k):
    x = self.root
    y = None
    z = Node(k)
    while x is not None:
      y = x
      if z.key < y.key:
        x = x.left
      elif y.key < z.key:
        x = x.right
    
    if y is None:
      # 初回値
      self.root = z
    else:
      if z.key < y.key:
        y.left = z
      elif y.key < z.key:
        y.right = z
  """      
  def inorder(self, r):
    # 中間巡回順で出力
    if r != None:
      self.inorder(r.left)
      print(" {}".format(r.key), end="")
      self.inorder(r.right)
  """    

  def preorder(self, r, lis):
    # 先行巡回順で出力
    if r != None:
      lis.append(r.key)
      self.preorder(r.left, lis)
      self.preorder(r.right, lis)

    
n = int(input())
bst = BST()
for _ in range(n):
  # query = [int(x) if re.match('[+|-]?\d', x) else x for x in input().split()]
  query = input().split()
  if query[0] == 'insert':
    bst.insert(int(query[1]))
  elif query[0] == 'print':
    root = bst.root
    lis = []
    bst.preorder(root, lis)
    print(" " + " ".join(list(map(str, sorted(lis)))))
    print(" " + " ".join(list(map(str, lis))))

Submission status: Accepted

Solution code:
class Node:
  key = None
  left = None
  right = None
  def __init__(self, k):
    self.key = k

class BST:
  root = None
  def insert(self, k):
    x = self.root
    y = None
    z = Node(k)
    while x is not None:
      y = x
      if z.key < y.key:
        x = x.left
      elif y.key < z.key:
        x = x.right
    
    if y is None:
      # 初回値
      self.root = z
    else:
      if z.key < y.key:
        y.left = z
      elif y.key < z.key:
        y.right = z

  def inorder(self, r, lis):
    # 中間巡回順で出力
    if r != None:
      self.inorder(r.left, lis)
      lis.append(r.key)
      self.inorder(r.right, lis)


  def preorder(self, r, lis):
    # 先行巡回順で出力
    if r != None:
      lis.append(r.key)
      self.preorder(r.left, lis)
      self.preorder(r.right, lis)

    
n = int(input())
bst = BST()
for _ in range(n):
  # query = [int(x) if re.match('[+|-]?\d', x) else x for x in input().split()]
  query = input().split()
  if query[0] == 'insert':
    bst.insert(int(query[1]))
  elif query[0] == 'print':
    root = bst.root
    in_lis = []
    pre_lis = []
    bst.preorder(root, pre_lis)
    bst.inorder(root, in_lis)
    print(" " + " ".join(list(map(str, in_lis))))
    print(" " + " ".join(list(map(str, pre_lis))))

Submission status: Accepted

Solution code:
# -*- coding: utf-8 -*-
"""
Created on Sat Mar  2 17:11:49 2019

@author: Yamazaki Kenichi
"""

m = int(input())
A = [list(input().split()) for i in range(m)]

T = [[-1,-1,-1,-1]]
def insert(T,u,x):
    if T[0][3] == -1:
        T[0][3] = x
        return
    if x < T[u][3]:
        if T[u][1] == -1:
            T[u][1] = len(T)
            T.append([u,-1,-1,x])
        else:
            insert(T,T[u][1],x)
    else:
        if T[u][2] == -1:
            T[u][2] = len(T)
            T.append([u,-1,-1,x])
        else:
            insert(T,T[u][2],x)
def ino(u):
    if T[u][1] != -1:
        ino(T[u][1])
    ino_res.append(str(T[u][3]))
    if T[u][2] != -1:
        ino(T[u][2])
def pre(u):
    pre_res.append(str(T[u][3]))
    if T[u][1] != -1:
        pre(T[u][1])
    if T[u][2] != -1:
        pre(T[u][2])
def find(u,x):
    if x == T[u][3]:
        return True
    elif x < T[u][3]:
        if T[u][1] == -1:
            return False
        return find(T[u][1],x)
    else:
        if T[u][2] == -1:
            return False
        return find(T[u][2],x)
for c in A:
    if c[0] == 'insert':
        insert(T,0,int(c[1]))
    elif c[0] == 'find':
        print('yes') if find(0,int(c[1])) else print('no')
    else:
        ino_res = []
        ino(0)
        pre_res = []
        pre(0)
        print(' '+' '.join(ino_res))
        print(' '+' '.join(pre_res))

Submission status: Accepted

Solution code:
class Node:
    def __init__(self, key):
        self.key = key
        self.parent = None
        self.left = None
        self.right = None

class Tree:

    def __init__(self):
        self.root = None

    def insert(self, node):
        y = None
        x = self.root

        while x is not None:
            y = x
            if node.key <= x.key:
                x = x.left
            else:
                x = x.right

        if y is None:
            self.root = node
        elif node.key < y.key:
            y.left = node
        else:
            y.right = node

    def print_in_order(self, node):
        if node is None:
            return
        self.print_in_order(node.left)
        print(' ' + str(node.key), end='')
        self.print_in_order(node.right)

    def print_pre_order(self, node):
        if node is None:
            return
        print(' ' + str(node.key), end='')
        self.print_pre_order(node.left)
        self.print_pre_order(node.right)

tree = Tree()
m = int(input())
for i in range(m):
    line = input().split()
    if line[0] == 'print':
        tree.print_in_order(tree.root)
        print('')
        tree.print_pre_order(tree.root)
        print('')
    else:
        key = line[1]
        tree.insert(Node(int(key)))

Submission status: Accepted

Solution code:
class Node:
    def __init__(self, key):
        self.key = key
        self.parent = None
        self.left = None
        self.right = None
class Tree:
    def __init__(self):
        self.root = None
        self.inorder = []
        self.preorder = []

    def insert(self, node):

        p = None
        x = self.root        
        while x is not None:
            p = x
            # print(node.key, x.key)
            if node.key <= x.key:
                x = x.left
            else:
                x = x.right

        # insertするnodeの親を設定
        node.parent = p

        if p is None:
            self.root = node
        else:
            # insertするnodeを親のleftかrightに設定
            if node.key <= p.key:
                # print('leftに設定')
                p.left = node
            else:
                # print('rightに設定')
                p.right = node


    def print_inorder(self):
        self.inorder = []
        self.inorder_traverse(self.root)
        print(' ' + ' '.join(map(str, self.inorder)))

    def print_preorder(self):
        self.preorder = []
        self.preorder_traverse(self.root)
        print(' ' + ' '.join(map(str, self.preorder)))

    def inorder_traverse(self, node):
        if node is None:
            return
        self.inorder_traverse(node.left)
        self.inorder.append(node.key)
        self.inorder_traverse(node.right)

    def preorder_traverse(self, node):
        if node is None:
            return
        self.preorder.append(node.key)
        self.preorder_traverse(node.left)
        self.preorder_traverse(node.right)

tree = Tree()
m = int(input())
for i in range(m):
    line = input().split()
    if line[0] == 'print':
        tree.print_inorder()
        tree.print_preorder()
    elif line[0] == 'insert':
        key = int(line[1])
        tree.insert(Node(key))
    # elif line[0] == 'find':
    #     key = int(line[1])
    #     if tree.find(key):
    #         print('yes')
    #     else:
    #         print('no')
    # elif line[0] == 'delete':
    #     print("current tree----")
    #     print(tree.root.key)
    #     print(tree.root.left.key)
    #     print(tree.root.left.right.key)
    #     print("current tree----")
    #     key = int(line[1])
    #     node = tree.find(key)
    #     tree.delete(node)

Submission status: Accepted

Solution code:
class Node():
    def __init__(self, key):
        self.key = key
        self.left = self.right = None
        
def insert(key):
    global root

    x = root
    y = None
    while x:x, y = x.left if key < x.key else x.right , x
    if y == None:root = Node(key)
    elif y.key < key:y.right = Node(key)
    else:y.left = Node(key)
        
        
def pre(node):
    if node == None:return
    print('',node.key, end = '');pre(node.left);pre(node.right)
    
def ino(node):
    if node == None:return
    ino(node.left);print('',node.key,end='');ino(node.right)


n = int(input())
root = None
for j in range(n):
    s, *i = input().split()
    if s[0] == 'i':insert(int(i[0]))
    else:
        ino(root);print('');pre(root);print()

Submission status: Accepted

Solution code:
class Node():
    def __init__(self, key):
        self.key = key
        self.left = self.right = None
        
def insert(key):
    global root

    x = root
    y = None
    while x:x, y = x.left if key < x.key else x.right , x
    if y == None:root = Node(key)
    elif y.key < key:y.right = Node(key)
    else:y.left = Node(key)
        
        
def pre(node):
    if node == None:return
    print('',node.key, end = '');pre(node.left);pre(node.right)
    
def ino(node):
    if node == None:return
    ino(node.left);print('',node.key,end='');ino(node.right)


n = int(input())
root = None
for j in range(n):
    s, *i = input().split()
    if s[0] == 'i':insert(int(i[0]))
    else:
        ino(root);print();pre(root);print()

Submission status: Accepted

Solution code:
import sys
class Tree():
    def __init__(self):
        self.root = None
    def insert(self, key):
        z = Node(key)
        y = None
        x = self.root
        while x:
            y = x
            if z.key < x.key:
                x = x.left
            else:
                x = x.right
        z.parent = y
        if y == None:
            self.root = z
        elif z.key < y.key:
            y.left = z
        else:
            y.right = z
    def print(self):
        print('',' '.join(map(str, self.root.inwalk())))
        print('',' '.join(map(str, self.root.prewalk())))
    
class Node():
    def __init__(self, key):
        self.key = key
        self.parent = self.left = self.right = None
    def prewalk(self):
        ret = [self.key]
        if self.left:
            ret += self.left.prewalk()
        if self.right:
            ret += self.right.prewalk()
        return ret
    def inwalk(self):
        ret = []
        if self.left:
            ret += self.left.inwalk()
        ret += [self.key]
        if self.right:
            ret += self.right.inwalk()
        return ret
tree = Tree()
n = sys.stdin.readline()
for line in sys.stdin:
    if line[0] == 'i':
        tree.insert(int(line.split()[1]))
    else:
        tree.print()

Submission status: Accepted

Solution code:
import sys

class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left = self.right = None

class BST:
    def __init__(self):
        self.root = None
    
    def insert(self, node):
        def helper(root):
            y, x = None, root
            while isinstance(x, TreeNode):
                y = x
                if node.val < x.val:
                    x = x.left
                else:
                    x = x.right
            if y is None:
                root = node
            elif node.val < y.val:
                y.left = node
            else:
                y.right = node
            return root
            
        self.root = helper(self.root)
    
    def inorder(self):
        def helper(root):
            return [] if root is None else helper(root.left) + [root.val] + helper(root.right)
        return helper(self.root)

    def preorder(self):
        def helper(root):
            return [] if root is None else [root.val] + helper(root.left) + helper(root.right)
        return helper(self.root)

if __name__ == '__main__':
    q = sys.stdin.readline()
    q = int(q)
    bst = BST()
    for i in range(q):
        tmp = sys.stdin.readline()
        if tmp.startswith('print'):
            print ' ' + ' '.join(map(lambda x: str(x), bst.inorder()))
            print ' ' + ' '.join(map(lambda x: str(x), bst.preorder()))
        else:
            _, val = tmp.split()
            node = TreeNode(int(val))
            bst.insert(node)

Submission status: Accepted

Solution code:
#!/usr/bin/env python
from __future__ import division, print_function
from sys import stdin
 
 
class Node(object):
    def __init__(self, key=None):
        self.key = key
        self.parent = None
        self.left = None
        self.right = None
 
 
def tree_insert(top, z):
    y = None
    x = top
    while isinstance(x, Node):
        y = x
        if z.key < x.key:
            x = x.left
        else:
            x = x.right
    z.parent = y
    if y is None:
        top = z
    elif z.key < y.key:
        y.left = z
    else:
        y.right = z
    return top
 
 
def inorder_walk(node):
    if node.left:
        inorder_walk(node.left)
    print('', node.key, end='')
    if node.right:
        inorder_walk(node.right)
 
 
def preorder_walk(node):
    print('', node.key, end='')
    if node.left:
        preorder_walk(node.left)
    if node.right:
        preorder_walk(node.right)
 
 
n = int(stdin.readline())
 
top = None
for _ in range(n):
    cmd = stdin.readline()
    if cmd.startswith('i'):
        key = int(cmd[7:])
        #assert -2000000000 <= key <= 2000000000
        top = tree_insert(top, Node(key))
    else:
        inorder_walk(top)
        print()
        preorder_walk(top)
        print()