leetcode 222. Number of nodes of a complete binary tree (required)

Problem description ：

Give a completely binary tree , Find out the number of nodes of the tree .

explain ：

The definition of a complete binary tree is as follows ： In a complete binary tree , Except that the lowest node may not be full , The number of nodes in each layer reaches the maximum , And the nodes of the lowest layer are concentrated in the leftmost positions of the layer . If the bottom layer is No h layer , Then the layer contains 1~ 2h Nodes .

Example :

Input :
    1
   / \
  2   3
 / \  /
4  5 6

Output : 6

Ideas ：

Find the number of nodes of a complete binary tree

Code up , Take it to run ：

package com.onlyqi.test03.erfen;

/**
 * @author onlyqi
 * @date 2022/7/12 14:44
 * @description
 */
public class Test6 {
    public static Integer num =0;
    public static void main(String[] args) {
        TreeNode treeNode1 = new TreeNode(1);
        TreeNode treeNode2 = new TreeNode(2);
        TreeNode treeNode3 = new TreeNode(3);
        TreeNode treeNode4 = new TreeNode(4);
        TreeNode treeNode5 = new TreeNode(5);
        TreeNode treeNode6 = new TreeNode(6);
        treeNode2.setLeft(treeNode6);
        treeNode3.setLeft(treeNode4);
        treeNode3.setRight(treeNode5);
        treeNode1.setLeft(treeNode3);
        treeNode1.setRight(treeNode2);
        System.out.println("========================"+count(treeNode1));
    }

    public static Integer count(TreeNode treeNode) {
        if (treeNode != null) {
            // Access the root node 
            num=num+1;
            // Access the left node 
            count(treeNode.getLeft());
            // Access the right node 
            count(treeNode.getRight());
        }
        return num;
    }
}

class TreeNode {
    private Integer value;
    private TreeNode left;
    private TreeNode right;
    public Integer getValue() {
        return value;
    }

    public void setValue(Integer value) {
        this.value = value;
    }

    public TreeNode getLeft() {
        return left;
    }

    public void setLeft(TreeNode left) {
        this.left = left;
    }

    public TreeNode getRight() {
        return right;
    }

    public void setRight(TreeNode right) {
        this.right = right;
    }

    public TreeNode(Integer value) {
        this.value = value;
    }

}

Running results ：

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