Print binary tree structure with its contents

Write an efficient algorithm to print a binary tree structure in standard output.

Print Binary Tree Generated Binary Tree

For example, a binary tree on the left can be displayed as a binary tree on the right programmatically. The following code in C++, Java, and Python serves as an excellent helper function to tree problems for printing a binary tree or BST:

C++

#include <iostream>

#include <string>

using namespace std;

// Data structure to store a binary tree node

struct Node

{

int data;

Node *left, *right;

Node(int data)

{

this->data = data;

this->left = this->right = nullptr;

}

};

struct Trunk

{

Trunk *prev;

string str;

Trunk(Trunk *prev, string str)

{

this->prev = prev;

this->str = str;

}

};

// Helper function to print branches of the binary tree

void showTrunks(Trunk *p)

{

if (p == nullptr) {

return;

}

showTrunks(p->prev);

cout << p->str;

}

void printTree(Node* root, Trunk *prev, bool isLeft)

{

if (root == nullptr) {

return;

}

string prev_str = " ";

Trunk *trunk = new Trunk(prev, prev_str);

printTree(root->right, trunk, true);

if (!prev) {

trunk->str = "———";

}

else if (isLeft)

{

trunk->str = ".———";

prev_str = " |";

}

else {

trunk->str = "`———";

prev->str = prev_str;

}

showTrunks(trunk);

cout << " " << root->data << endl;

if (prev) {

prev->str = prev_str;

}

trunk->str = " |";

printTree(root->left, trunk, false);

}

int main()

{

// Construct above tree

Node* root = new Node(1);

root->left = new Node(2);

root->right = new Node(3);

root->left->left = new Node(4);

root->left->right = new Node(5);

root->right->left = new Node(6);

root->right->right = new Node(7);

root->left->left->left = new Node(8);

root->left->left->right = new Node(9);

root->left->right->left = new Node(10);

root->left->right->right = new Node(11);

root->right->left->left = new Node(12);

root->right->left->right = new Node(13);

root->right->right->left = new Node(14);

root->right->right->right = new Node(15);

// print constructed binary tree

printTree(root, nullptr, false);

return 0;

}

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Java

class Trunk

{

Trunk prev;

String str;

Trunk(Trunk prev, String str)

{

this.prev = prev;

this.str = str;

}

};

// A Binary Tree Node

class Node

{

int data;

Node left, right;

Node() {}

Node(int data)

{

this.data = data;

this.left = this.right = null;

}

class Main

{

public static void showTrunks(Trunk p)

{

if (p == null) {

return;

}

showTrunks(p.prev);

System.out.print(p.str);

}

public static void printTree(Node root, Trunk prev, boolean isLeft)

{

if (root == null) {

return;

}

String prev_str = " ";

Trunk trunk = new Trunk(prev, prev_str);

printTree(root.right, trunk, true);

if (prev == null) {

trunk.str = "———";

}

else if (isLeft) {

trunk.str = ".———";

prev_str = " |";

}

else {

trunk.str = "`———";

prev.str = prev_str;

}

showTrunks(trunk);

System.out.println(" " + root.data);

if (prev != null) {

prev.str = prev_str;

}

trunk.str = " |";

printTree(root.left, trunk, false);

}

public static void main(String[] args)

{

// Construct above tree

Node root = new Node(1);

root.left = new Node(2);

root.right = new Node(3);

root.left.left = new Node(4);

root.left.right = new Node(5);

root.right.left = new Node(6);

root.right.right = new Node(7);

root.left.left.left = new Node(8);

root.left.left.right = new Node(9);

root.left.right.left = new Node(10);

root.left.right.right = new Node(11);

root.right.left.left = new Node(12);

root.right.left.right = new Node(13);

root.right.right.left = new Node(14);

root.right.right.right = new Node(15);

// print constructed binary tree

printTree(root, null, false);

}

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Python

# A Binary Tree Node

class Node:

def __init__(self, data=None, left=None, right=None):

self.data = data

self.left = left

self.right = right

class Trunk:

def __init__(self, prev=None, str=None):

self.prev = prev

self.str = str

def showTrunks(p):

if p is None:

return

showTrunks(p.prev)

print(p.str, end='')

def printTree(root, prev, isLeft):

if root is None:

return

prev_str = ' '

trunk = Trunk(prev, prev_str)

printTree(root.right, trunk, True)

if prev is None:

trunk.str = '———'

elif isLeft:

trunk.str = '.———'

prev_str = ' |'

else:

trunk.str = '`———'

prev.str = prev_str

showTrunks(trunk)

print(' ' + str(root.data))

if prev:

prev.str = prev_str

trunk.str = ' |'

printTree(root.left, trunk, False)

if __name__ == '__main__':

# Construct above tree

root = Node(1)

root.left = Node(2)

root.right = Node(3)

root.left.left = Node(4)

root.left.right = Node(5)

root.right.left = Node(6)

root.right.right = Node(7)

root.left.left.left = Node(8)

root.left.left.right = Node(9)

root.left.right.left = Node(10)

root.left.right.right = Node(11)

root.right.left.left = Node(12)

root.right.left.right = Node(13)

root.right.right.left = Node(14)

root.right.right.right = Node(15)

# print constructed binary tree

printTree(root, None, False)

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