"Programmer Code Interview Guide" Chapter 3 Binary Tree Questions Counting the Number of Nodes in a Complete Binary Tree

topic

统计完全二叉树的节点数

java code

package com.lizhouwei.chapter3;


/**
 * @Description:统计完全二叉树的节点数
 * @Author: lizhouwei
 * @CreateDate: 2018/4/16 21:47
 * @Modify by:
 * @ModifyDate:
 */
public class Chapter3_24 {

    public int nodeNum(Node head) {
        if (head == null) {
            return 0;
        }
        return bs(head, 1, getLevel(head, 1));
    }

    private int bs(Node head, int level, int h) {
        if (level == h) {
            return 1;
        }
        if (getLevel(head.right, level + 1) == h) {
            return (1 << (h - level)) + bs(head.right, level + 1, h);
        } else {
            return (1 << (h - level - 1)) + bs(head.left, level + 1, h);
        }
    }

    private int getLevel(Node head, int level) {
        while (head != null) {
            level++;
            head = head.left;
        }
        return level - 1;
    }

    //测试
    public static void main(String[] args) {
        Chapter3_24 chapter = new Chapter3_24();
        Node head = new Node(5);
        head.left = new Node(3);
        head.right = new Node(7);
        head.left.left = new Node(2);
        head.left.right = new Node(4);
        head.right.left = new Node(6);
        head.right.right = new Node(8);
        head.left.left.left = new Node(1);
        System.out.print("中序数组：");
        NodeUtil.inOrder(head);
        System.out.print("节点个数:" + chapter.nodeNum(head));
    }
}

result