Print Binary Search Tree in Min Max Fashion

25 Oct, 2021
Given a Binary Search Tree (BST), the task is to print the BST in min-max fashion. What is min-max fashion? A min-max fashion means you have to print the maximum node first then the minimum then the second maximum then the second minimum and so on.
Examples: 
Input:                
         100                            
        /   \    
      20     500     
     /  \                      
    10   30 
          \   
           40
Output: 10 500 20 100 30 40

Input:
         40                            
        /   \    
      20     50     
     /  \      \               
    10   35     60
        /      /   
      25      55
Output: 10 60 20 55 25 50 35 40 
Approach:  
Create an array inorder[] and store the inorder traversal of the given binary search tree.Since the inorder traversal of the binary search tree is sorted in ascending, initialise i = 0 and j = n – 1.Print inorder[i] and update i = i + 1.Print inorder[j] and update j = j – 1.Repeat steps 3 and 4 until all the elements have been printed.
Create an array inorder[] and store the inorder traversal of the given binary search tree.
Since the inorder traversal of the binary search tree is sorted in ascending, initialise i = 0 and j = n – 1.
Print inorder[i] and update i = i + 1.
Print inorder[j] and update j = j – 1.
Repeat steps 3 and 4 until all the elements have been printed.
Below is the implementation of the above approach:  
C++
Java
Python3
C#
Javascript
// C++ implementation of the approach#include <iostream>using namespace std; // Structure of each node of BSTstruct node {    int key;    struct node *left, *right;}; // A utility function to create a new BST nodenode* newNode(int item){    node* temp = new node();    temp->key = item;    temp->left = temp->right = NULL;    return temp;} /* A utility function to insert a newnode with given key in BST */struct node* insert(struct node* node, int key){    /* If the tree is empty, return a new node */    if (node == NULL)        return newNode(key);     /* Otherwise, recur down the tree */    if (key < node->key)        node->left = insert(node->left, key);    else if (key > node->key)        node->right = insert(node->right, key);     /* return the (unchanged) node pointer */    return node;} // Function to return the size of the treeint sizeOfTree(node* root){    if (root == NULL) {        return 0;    }     // Calculate left size recursively    int left = sizeOfTree(root->left);     // Calculate right size recursively    int right = sizeOfTree(root->right);     // Return total size recursively    return (left + right + 1);} // Utility function to print the// Min max order of BSTvoid printMinMaxOrderUtil(node* root, int inOrder[],                          int& index){     // Base condition    if (root == NULL) {        return;    }     // Left recursive call    printMinMaxOrderUtil(root->left, inOrder, index);     // Store elements in inorder array    inOrder[index++] = root->key;     // Right recursive call    printMinMaxOrderUtil(root->right, inOrder, index);} // Function to print the// Min max order of BSTvoid printMinMaxOrder(node* root){    // Store the size of BST    int numNode = sizeOfTree(root);     // Take auxiliary array for storing    // The inorder traversal of BST    int inOrder[numNode + 1];    int index = 0;     // Function call for printing    // element in min max order    printMinMaxOrderUtil(root, inOrder, index);    int i = 0;    index--;     // While loop for printing elements    // In front last order    while (i < index) {        cout << inOrder[i++] << " "             << inOrder[index--] << " ";    }    if (i == index) {        cout << inOrder[i] << endl;    }} // Driver codeint main(){    struct node* root = NULL;    root = insert(root, 50);    insert(root, 30);    insert(root, 20);    insert(root, 40);    insert(root, 70);    insert(root, 60);    insert(root, 80);     printMinMaxOrder(root);     return 0;}
// Java implementation of the approachclass GFG{ // Structure of each node of BSTstatic class node{    int key;    node left, right;};static int index; // A utility function to create a new BST nodestatic node newNode(int item){    node temp = new node();    temp.key = item;    temp.left = temp.right = null;    return temp;} /* A utility function to insert a newnode with given key in BST */static node insert(node node, int key){    /* If the tree is empty,    return a new node */    if (node == null)        return newNode(key);     /* Otherwise, recur down the tree */    if (key < node.key)        node.left = insert(node.left, key);    else if (key > node.key)        node.right = insert(node.right, key);     /* return the (unchanged) node pointer */    return node;} // Function to return the size of the treestatic int sizeOfTree(node root){    if (root == null)    {        return 0;    }     // Calculate left size recursively    int left = sizeOfTree(root.left);     // Calculate right size recursively    int right = sizeOfTree(root.right);     // Return total size recursively    return (left + right + 1);} // Utility function to print the// Min max order of BSTstatic void printMinMaxOrderUtil(node root,                                 int inOrder[]){     // Base condition    if (root == null)    {        return;    }     // Left recursive call    printMinMaxOrderUtil(root.left, inOrder);     // Store elements in inorder array    inOrder[index++] = root.key;     // Right recursive call    printMinMaxOrderUtil(root.right, inOrder);} // Function to print the// Min max order of BSTstatic void printMinMaxOrder(node root){    // Store the size of BST    int numNode = sizeOfTree(root);     // Take auxiliary array for storing    // The inorder traversal of BST    int []inOrder = new int[numNode + 1];     // Function call for printing    // element in min max order    printMinMaxOrderUtil(root, inOrder);    int i = 0;    index--;     // While loop for printing elements    // In front last order    while (i < index)    {        System.out.print(inOrder[i++] + " " +                         inOrder[index--] + " ");    }    if (i == index)    {        System.out.println(inOrder[i]);    }} // Driver codepublic static void main(String[] args){    node root = null;    root = insert(root, 50);    insert(root, 30);    insert(root, 20);    insert(root, 40);    insert(root, 70);    insert(root, 60);    insert(root, 80);     printMinMaxOrder(root);}} // This code is contributed by 29AjayKumar
# Python3 implementation of the approach # Structure of each node of BSTclass Node:    def __init__(self,key):        self.left = None        self.right = None        self.val = key         def insert(root,node):    if root is None:        root = Node(node)    else:        if root.val < node:            if root.right is None:                root.right = Node(node)            else:                insert(root.right, node)        else:            if root.left is None:                root.left = Node(node)            else:                insert(root.left, node)                 # Function to return the size of the treedef sizeOfTree(root):     if root == None:        return 0         # Calculate left size recursively    left = sizeOfTree(root.left)     # Calculate right size recursively    right = sizeOfTree(root.right);     # Return total size recursively    return (left + right + 1) # Utility function to print the# Min max order of BSTdef printMinMaxOrderUtil(root, inOrder, index):     # Base condition    if root == None:        return     # Left recursive call    printMinMaxOrderUtil(root.left, inOrder, index)     # Store elements in inorder array    inOrder[index[0]] = root.val    index[0] += 1     # Right recursive call    printMinMaxOrderUtil(root.right, inOrder, index) # Function to print the# Min max order of BSTdef printMinMaxOrder(root):         # Store the size of BST    numNode = sizeOfTree(root);     # Take auxiliary array for storing    # The inorder traversal of BST    inOrder = [0] * (numNode + 1)    index = 0     # Function call for printing    # element in min max order    ref = [index]    printMinMaxOrderUtil(root, inOrder, ref)    index = ref[0]    i = 0;    index -= 1     # While loop for printing elements    # In front last order    while (i < index):                 print (inOrder[i], inOrder[index], end = ' ')        i += 1        index -= 1         if i == index:        print(inOrder[i])     # Driver Coderoot = Node(50)insert(root, 30)insert(root, 20)insert(root, 40)insert(root, 70)insert(root, 60)insert(root, 80) printMinMaxOrder(root)     # This code is contributed by Sadik Ali
// C# implementation of the approachusing System; class GFG{ // Structure of each node of BSTclass node{    public int key;    public node left, right;};static int index; // A utility function to create a new BST nodestatic node newNode(int item){    node temp = new node();    temp.key = item;    temp.left = temp.right = null;    return temp;} /* A utility function to insert a newnode with given key in BST */static node insert(node node, int key){    /* If the tree is empty,    return a new node */    if (node == null)        return newNode(key);     /* Otherwise, recur down the tree */    if (key < node.key)        node.left = insert(node.left, key);    else if (key > node.key)        node.right = insert(node.right, key);     /* return the (unchanged) node pointer */    return node;} // Function to return the size of the treestatic int sizeOfTree(node root){    if (root == null)    {        return 0;    }     // Calculate left size recursively    int left = sizeOfTree(root.left);     // Calculate right size recursively    int right = sizeOfTree(root.right);     // Return total size recursively    return (left + right + 1);} // Utility function to print the// Min max order of BSTstatic void printMinMaxOrderUtil(node root,                                  int []inOrder){     // Base condition    if (root == null)    {        return;    }     // Left recursive call    printMinMaxOrderUtil(root.left, inOrder);     // Store elements in inorder array    inOrder[index++] = root.key;     // Right recursive call    printMinMaxOrderUtil(root.right, inOrder);} // Function to print the// Min max order of BSTstatic void printMinMaxOrder(node root){    // Store the size of BST    int numNode = sizeOfTree(root);     // Take auxiliary array for storing    // The inorder traversal of BST    int []inOrder = new int[numNode + 1];     // Function call for printing    // element in min max order    printMinMaxOrderUtil(root, inOrder);    int i = 0;    index--;     // While loop for printing elements    // In front last order    while (i < index)    {        Console.Write(inOrder[i++] + " " +                      inOrder[index--] + " ");    }    if (i == index)    {        Console.WriteLine(inOrder[i]);    }} // Driver codepublic static void Main(String[] args){    node root = null;    root = insert(root, 50);    insert(root, 30);    insert(root, 20);    insert(root, 40);    insert(root, 70);    insert(root, 60);    insert(root, 80);     printMinMaxOrder(root);}} // This code is contributed by PrinciRaj1992
<script> // Javascript implementation of the approach // Structure of each node of BSTclass node{    constructor()    {        this.key = 0;        this.left = null;        this.right = null;    }}; var index = 0; // A utility function to create a new BST nodefunction newNode(item){    var temp = new node();    temp.key = item;    temp.left = temp.right = null;    return temp;} // A utility function to insert a new// node with given key in BSTfunction insert(node, key){         /* If the tree is empty,    return a new node */    if (node == null)        return newNode(key);     /* Otherwise, recur down the tree */    if (key < node.key)        node.left = insert(node.left, key);    else if (key > node.key)        node.right = insert(node.right, key);     /* return the (unchanged) node pointer */    return node;} // Function to return the size of the treefunction sizeOfTree(root){    if (root == null)    {        return 0;    }     // Calculate left size recursively    var left = sizeOfTree(root.left);     // Calculate right size recursively    var right = sizeOfTree(root.right);     // Return total size recursively    return (left + right + 1);} // Utility function to print the// Min max order of BSTfunction printMinMaxOrderUtil(root, inOrder){         // Base condition    if (root == null)    {        return;    }     // Left recursive call    printMinMaxOrderUtil(root.left, inOrder);     // Store elements in inorder array    inOrder[index++] = root.key;     // Right recursive call    printMinMaxOrderUtil(root.right, inOrder);} // Function to print the// Min max order of BSTfunction printMinMaxOrder(root){         // Store the size of BST    var numNode = sizeOfTree(root);     // Take auxiliary array for storing    // The inorder traversal of BST    var inOrder = Array(numNode+1);     // Function call for printing    // element in min max order    printMinMaxOrderUtil(root, inOrder);    var i = 0;    index--;     // While loop for printing elements    // In front last order    while (i < index)    {        document.write(inOrder[i++] + " " +                       inOrder[index--] + " ");    }    if (i == index)    {        document.write(inOrder[i]);    }} // Driver codevar root = null;root = insert(root, 50);insert(root, 30);insert(root, 20);insert(root, 40);insert(root, 70);insert(root, 60);insert(root, 80); printMinMaxOrder(root); // This code is contributed by noob2000 </script>
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chsadik99
29AjayKumar
princiraj1992
noob2000
prachisoda1234
Inorder Traversal
Binary Search Tree
Recursion
Tree
Recursion
Binary Search Tree
Tree
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