Recursive and non-recursive traversal of Binary Trees (for example)

Recursive and non-recursive traversal of Binary Trees (for example)

Binary tree traversal mainly involves Recursive Implementation and non-Recursive Implementation. Recursive Implementation is easy to understand. Non-Recursive Implementation mainly utilizes the stack idea, and then comes first and foremost, in this article, the non-recursive traversal of Binary Trees is implemented mainly by using the functions that the consumer list can be used as a stack. An example is as follows:

Package com. sheepmu; import java. util. optional list; public class BinaryTree {private TreeNode root; // root node public BinaryTree () {} public BinaryTree (TreeNode root) {this. root = root;} public TreeNode getRoot () {return root;} public void setRoot (TreeNode root) {this. root = root;}/*** node class */private static class TreeNode {private String data = null; // private TreeNode left of data; // reference of left node privat E TreeNode right; // reference of the right node public TreeNode (String data, TreeNode left, TreeNode right) // constructor of the node, the node created in the test function uses it {this. data = data; this. left = left; this. right = right;} public String getData () // get and set methods of the node class {return data;} public void setData (String data) {this. data = data;} public TreeNode getLeft () {return left;} public void setLeft (TreeNode left) {this. left = left;} public TreeNode ge TRight () {return right;} public void setRight (TreeNode right) {this. right = right ;}/ ***** recursive pretraversal */public void preOrder (TreeNode node) {if (node! = Null) {System. out. print (node. getData () + ""); preOrder (node. getLeft (); preOrder (node. getRight () ;}}/*** recursive traversal */public void inOrder (TreeNode node) {if (node! = Null) {inOrder (node. getLeft (); System. out. print (node. getData () + ""); inOrder (node. getRight () ;}}/*** recursive subsequent traversal */public void postOrder (TreeNode node) {if (node! = Null) {postOrder (node. getLeft (); postOrder (node. getRight (); System. out. print (node. getData () + "") ;}}/*** non-recursive pre-continuation traversal */public void preOrderNoRecursion () {revoke list
 
  
Stack = new consumer list
  
   
(); Stack. push (root); TreeNode current = null; while (! Stack. isEmpty () {current = stack. pop (); System. out. print (current. data + ""); if (current. getRight ()! = Null) stack. push (current. getRight (); if (current. getLeft ()! = Null) stack. push (current. getLeft ();} System. out. println ();}/*** continuous traversal in non-recursion */public void inorderNoRecursion () {revoke list
   
    
Stack = new consumer list
    
     
(); TreeNode current = root; while (current! = Null |! Stack. isEmpty () {while (current! = Null) {stack. push (current); current = current. getLeft ();} if (! Stack. isEmpty () {current = stack. pop (); System. out. print (current. data + ""); current = current. getRight () ;}} System. out. println ();}/*** non-recursive subsequent traversal */public void postorderNoRecursion () {TreeNode rNode = null; TreeNode current = root; history list
     
      
Stack = new consumer list
      
        (); While (current! = Null |! Stack. isEmpty () {while (current! = Null) {stack. push (current); current = current. getLeft () ;}current = stack. pop (); while (current! = Null & (current. getRight () = null | current. getRight () = rNode) {System. out. print (current. data + ""); rNode = current; if (stack. isEmpty () {System. out. println (); return;} current = stack. pop ();} stack. push (current); current = current. getRight () ;}} public static void main (String [] args) {TreeNode l2 = new TreeNode ("E", null, null ); // The Five Elements construct a binary tree TreeNode r2 = new TreeNode ("D", null, null); TreeNode l1 = new TreeNode ("B", null, r2 ); // TreeNode r1 = new TreeNode ("C", l2, null) on the left subtree of the root node; // TreeNode root = new TreeNode ("A", l1, r1); // create the root node BinaryTree bt = new BinaryTree (root); System. out. print ("recursive pre-order traversal ------->"); bt. preOrder (bt. getRoot (); System. out. print ("non-recursive pre-order traversal ------->"); bt. postorderNoRecursion (); System. out. print ("recursive ordinal traversal ------->"); bt. inOrder (bt. getRoot (); System. out. print ("non-recursive middle-order traversal ------->"); bt. inorderNoRecursion (); System. out. print ("recursive post-order traversal ------->"); bt. postOrder (bt. getRoot (); System. out. print ("non-recursive post-order traversal ------->"); bt. postorderNoRecursion ();}}
      
     
    
   
  
 

Recursive pre-order traversal -------> a B d c e non-recursive pre-order traversal -------> D B E C
Recursive middle-order traversal -------> B d a e c Non-recursive middle-order traversal -------> B D A E C
Recursive post-order traversal -------> d B e c a non-recursive post-order traversal -------> D B E C