treetraversal.java

class Node 
{ 
    int key; 
    Node left, right; 
  
    public Node(int item) 
    { 
        key = item; 
        left = right = null; 
    } 
} 
  
class BinaryTree 
{ 
    // Root of Binary Tree 
    Node root; 
  
    BinaryTree() 
    { 
        root = null; 
    } 
  
    /* Given a binary tree, print its nodes according to the 
      "bottom-up" postorder traversal. */
    void printPostorder(Node node) 
    { 
        if (node == null) 
            return; 
  
        // first recur on left subtree 
        printPostorder(node.left); 
  
        // then recur on right subtree 
        printPostorder(node.right); 
  
        // now deal with the node 
        System.out.print(node.key + " "); 
    } 
  
    /* Given a binary tree, print its nodes in inorder*/
    void printInorder(Node node) 
    { 
        if (node == null) 
            return; 
  
        /* first recur on left child */
        printInorder(node.left); 
  
        /* then print the data of node */
        System.out.print(node.key + " "); 
  
        /* now recur on right child */
        printInorder(node.right); 
    } 
  
    /* Given a binary tree, print its nodes in preorder*/
    void printPreorder(Node node) 
    { 
        if (node == null) 
            return; 
  
        /* first print data of node */
        System.out.print(node.key + " "); 
  
        /* then recur on left sutree */
        printPreorder(node.left); 
  
        /* now recur on right subtree */
        printPreorder(node.right); 
    } 
  
    // Wrappers over above recursive functions 
    void printPostorder()  {     printPostorder(root);  } 
    void printInorder()    {     printInorder(root);   } 
    void printPreorder()   {     printPreorder(root);  } 
  
    // Driver method 
    public static void main(String[] args) 
    { 
        BinaryTree tree = new BinaryTree(); 
        tree.root = new Node(1); 
        tree.root.left = new Node(2); 
        tree.root.right = new Node(3); 
        tree.root.left.left = new Node(4); 
        tree.root.left.right = new Node(5); 
  
        System.out.println("Preorder traversal of binary tree is "); 
        tree.printPreorder(); 
  
        System.out.println("\nInorder traversal of binary tree is "); 
        tree.printInorder(); 
  
        System.out.println("\nPostorder traversal of binary tree is "); 
        tree.printPostorder(); 
    } 
} 
/*
  Time Complexity - O(N)
  Space Complexity - O(N)
  Input - Taken in the Code .
  Output- 
  Preorder traversal of binary tree is
  1 2 4 5 3 
  Inorder traversal of binary tree is
  4 2 5 1 3 
  Postorder traversal of binary tree is
  4 5 2 3 1
*/