tree data structure in c++ code example

Example 1: tree in c++ stl

// C++ STL library does not provide any non linear data structure like
// Trees and Graphs
// it only provides linear data structures like 
// vector , list , map , stack , queue etc..
// https://www.geeksforgeeks.org/binary-tree-data-structure/
// https://www.geeksforgeeks.org/graph-implementation-using-stl-for-competitive-programming-set-1-dfs-of-unweighted-and-undirected/

Example 2: java binary tree

public class BinaryTree {

    private int key;

    private BinaryTree left, right;

    /**
     * Simple constructor.
     *
     * @param key
     *     to set as key.
     */
    public BinaryTree(int key) {
        this.key = key;
    }

    /**
     * Extended constructor.
     *
     * @param key
     *     to set as key.
     * @param left
     *     to set as left child.
     * @param right
     *     to set as right child.
     */
    public BinaryTree(int key, BinaryTree left, BinaryTree right) {
        this.key = key;
        setLeft(left);
        setRight(right);
    }

    public int getKey() {
        return key;
    }

    /**
     * @return the left child.
     */
    public BinaryTree getLeft() {
        return left;
    }

    /**
     * @return the right child.
     */
    public BinaryTree getRight() {
        return right;
    }

    public boolean hasLeft() {
        return left != null;
    }

    public boolean hasRight() {
        return right != null;
    }

    //Return a String representation of the BinaryTree using level order traversal
    public String toString(){
        int h = height(this);
        int i;
        String result = "";
        for (i=1; i<=h; i++) {
            result += printGivenLevel(this, i);
        }
        return result;
    }

    //returns the number of nodes in the BinaryTree
    public int size(){
        return size(this);
    }

    public static int size(BinaryTree tree){
        if(tree == null) return 0;
        return 1 + size(tree.getLeft()) + size(tree.getRight());
    }

    public int height(){ return height(this);}

    public static int height(BinaryTree tree){
        if(tree == null) return 0;
        int left = height(tree.getLeft());
        int right = height(tree.getRight());
        return Math.max(left, right) + 1;
    }

    public String printGivenLevel (BinaryTree root ,int level) {
        if (root == null) return "";
        String result = "";
        if (level == 1) {
            result += root.getKey() + " ";
            return result;
        }else if (level > 1) {
            String left = printGivenLevel(root.left, level-1);
            String right = printGivenLevel(root.right, level-1);
            return left + right;
        }else{
            return "";
        }
    }

    /**
     * @param left
     *     to set
     */
    public void setLeft(BinaryTree left) {
        this.left = left;
    }

    /**
     * @param right
     *     to set
     */
    public void setRight(BinaryTree right) {
        this.right = right;
    }
}

Example 3: tree data structure

If root is NULL 
   then create root node
return

If root exists then
   compare the data with node.data
   
   while until insertion position is located

      If data is greater than node.data
         goto right subtree
      else
         goto left subtree

   endwhile 
   
   insert data
	
end If

Example 4: tree data structure

struct node {
   int data;   
   struct node *leftChild;
   struct node *rightChild;
};