# An example of a binary tree data structure in Java

• 2020-04-01 04:06:28
• OfStack

Let's look at a specific exercise:

The title
According to binary tree preorder traversal sequence, for example: 7, 7, 8 -, #, #, and 3, 6,, # 9, #, #, #, - 5, #, #, building a binary tree, and use before order, in sequence, after the order of traversal

code

``````
import java.util.Scanner;

public class BinaryTree {
public static String[] str;
public static int count;

static class TreeNode {
public String data;
TreeNode lchild;
TreeNode rchild;

public TreeNode(String x) {
this.data = x;
}
}

public static TreeNode createBtree() {
TreeNode root = null;

if (count >= str.length || str[count++].equals("#")) {
root = null;
} else {
root = new TreeNode(str[count - 1]);
root.lchild = createBtree();
root.rchild = createBtree();
}

return root;
}

public static void preTraverse(TreeNode root) {
if (root != null) {
System.out.print(root.data + " ");
preTraverse(root.lchild);
preTraverse(root.rchild);
}
}

public static void inTraverse(TreeNode root) {
if (root != null) {
inTraverse(root.lchild);
System.out.print(root.data + " ");
inTraverse(root.rchild);
}
}

public static void postTraverse(TreeNode root) {
if (root != null) {
postTraverse(root.lchild);
postTraverse(root.rchild);
System.out.print(root.data + " ");
}
}

public static void main(String args[]) {
Scanner cin = new Scanner(System.in);

while (cin.hasNext()) {
String s = cin.nextLine();
str = s.split(",");

count = 0;

TreeNode root = createBtree();

//The former sequence traversal
preTraverse(root);
System.out.println();

//In the sequence traversal
inTraverse(root);
System.out.println();

//After the sequence traversal
postTraverse(root);
System.out.println();
}
}
}
``````

The depth of the binary tree

The following is the implementation of the recursive algorithm of binary tree. The idea is that if is empty, its depth is 0; otherwise, its depth is equal to the maximum value of the depth of left subtree and right subtree plus 1:

``````
class Node{
String name;
Node left;
Node right;
public Node(String name) {
this.name = name;
}
@Override
public String toString() {
return name;
}
}
//Define a binary tree
class BinaryTree{
Node root;

public BinaryTree(){
root = null;
}
//For the sake of convenience, I'll just write an initial binary tree and see the previous log for details
public void initTree(){

Node node1 = new Node("a");
Node node2 = new Node("b");
Node node3 = new Node("c");
Node node4 = new Node("d");
Node node5 = new Node("e");
root = node1;
node1.left = node2;
node2.right = node3;
node1.right = node4;
node3.left = node5;
}
//Find the depth of the binary tree
int length(Node root){
int depth1;
int depth2;
if(root == null) return 0;
//Depth of the left subtree
depth1 = length(root.right);
//Depth of the right subtree
depth2 = length(root.left);
if(depth1>depth2)
return depth1+1;
else
return depth2+1;
}
}
public class TestMatch{

public static void main(String[] args) {
BinaryTree tree = new BinaryTree();
tree.initTree();
System.out.println(tree.length(tree.root));
}
}

``````

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