Implement binary tree using Java

A few days ago, someone asked me how to implement the post-Order Non-recursive traversal of Binary Trees. I didn't think of it for a moment. Today, I wrote all the operations related to binary trees, including creating them, in the middle order, the first order, the second order (recursive and non-recursive), the focus is on the Java first order to create a binary tree and the Second Order Non-recursive traversal implementation.

The following are the Implementation Details:CodeThe input is the input.txt file in the project directory. "#" indicates that the node is empty.

Package COM. algorithm. tree; import Java. io. file; import Java. io. filenotfoundexception; import Java. util. queue; import Java. util. imports; import Java. util. stack; import Java. util. concurrent. linkedblockingqueue; public class tree <t> {private node <t> root; public tree () {} public tree (node <t> root) {This. root = root;} // create a binary tree public void buildtree () {partition SCN = NULL; try {SCN = new partition (new file ("input.txt" );} Catch (filenotfoundexception e) {// todo auto-generated catch blocke. printstacktrace ();} root = createtree (root, SCN);} // first traverse and create a binary tree private node <t> createtree (node <t> node, scanner SCN) {string temp = SCN. next (); If (temp. trim (). equals ("#") {return NULL;} else {node = new node <t> (t) temp); node. setleft (createtree (node. getleft (), SCN); node. setright (createtree (node. getright (), SCN); Return node ;}}// In-order traversal (recursion) Public void inordertraverse () {inordertraverse (Root);} public void inordertraverse (node <t> node) {If (node! = NULL) {inordertraverse (node. getleft (); system. out. println (node. getvalue (); inordertraverse (node. getright () ;}}// the traversal in the middle order (non-recursion) Public void nrinordertraverse () {stack <node <t> stack = new stack <node <t> (); node <t> node = root; while (node! = NULL |! Stack. isempty () {While (node! = NULL) {stack. push (node); node = node. getleft ();} node = stack. pop (); system. out. println (node. getvalue (); node = node. getright () ;}/// first-order traversal (recursion) Public void preordertraverse () {preordertraverse (Root);} public void preordertraverse (node <t> node) {If (node! = NULL) {system. out. println (node. getvalue (); preordertraverse (node. getleft (); preordertraverse (node. getright () ;}}// first-order traversal (non-recursion) Public void nrpreordertraverse () {stack <node <t> stack = new stack <node <t> (); node <t> node = root; while (node! = NULL |! Stack. isempty () {While (node! = NULL) {system. out. println (node. getvalue (); stack. push (node); node = node. getleft ();} node = stack. pop (); node = node. getright () ;}/// post-order traversal (recursion) Public void postordertraverse () {postordertraverse (Root);} public void postordertraverse (node <t> node) {If (node! = NULL) {postordertraverse (node. getleft (); postordertraverse (node. getright (); system. out. println (node. getvalue () ;}}// subsequent traversal (non-recursive) Public void nrpostordertraverse () {stack <node <t> stack = new stack <node <t> (); node <t> node = root; node <t> prenode = NULL; // indicates the last accessed node while (node! = NULL |! Stack. isempty () {While (node! = NULL) {stack. push (node); node = node. getleft ();} node = stack. peek (); If (node. getright () = NULL | node. getright () = prenode) {system. out. println (node. getvalue (); node = stack. pop (); prenode = node; node = NULL;} else {node = node. getright () ;}}// traverse the public void leveltraverse () {leveltraverse (Root);} public void leveltraverse (node <t> node) {queue <node <t> queue = new linkedblockingqueue <node <t> (); Queue. Add (node); While (! Queue. isempty () {node <t> temp = queue. Poll (); If (temp! = NULL) {system. out. println (temp. getvalue (); queue. add (temp. getleft (); queue. add (temp. getright () ;}}}// Tree node class node <t> {private node <t> left; private node <t> right; private T value; public node () {} public node (node <t> left, node <t> right, T value) {This. left = left; this. right = right; this. value = value;} public node (T value) {This (null, null, value);} public node <t> getleft () {return left ;} public void setleft (node <t> left) {This. left = left;} public node <t> getright () {return right;} public void setright (node <t> right) {This. right = right;} public t getvalue () {return value;} public void setvalue (T value) {This. value = value ;}}

Test code:

 
Package COM. algorithm. tree; public class treetest {/*** @ Param ARGs */public static void main (string [] ARGs) {tree <integer> tree = new tree <integer> (); tree. buildtree (); system. out. println ("sequential traversal"); tree. inordertraverse (); tree. nrinordertraverse (); system. out. println ("subsequent traversal"); // tree. nrpostordertraverse (); tree. postordertraverse (); tree. nrpostordertraverse (); system. out. println ("sequential traversal"); tree. preordertraverse (); tree. nrpreordertraverse ();//}}
 

The younger brother is using generic type for the first time. Do not spray it in an inappropriate place.