Count Complete Tree Nodes （求完全二叉树节点树）

Count Complete Tree Nodes

Given a complete binary tree, count the number of nodes.


Definition of a complete binary tree from Wikipedia:

In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h.

说了那么多其实就是求完全二叉树的节点树

Thinking

首先我们要明白什么是完全二叉树（与满二叉树的区别）

满二叉树节点树为 2^H-1

+-优先级大于<<运算符

Code

[code]/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {

    public int countNodes(TreeNode root) {
        if(root==null) return 0;

        int left=getleftHigh(root.left);
        int right=getrightHigh(root.right);

        if(left==right){
            return (1<<(left+1))-1;
        }
        else{
            return countNodes(root.left)+countNodes(root.right)+1;
        }

    }
    public int  getleftHigh(TreeNode root)
    {
        int count =0;
        while(root!=null){
            count++;

            root=root.left;
        }
        return count;
    }
    public int  getrightHigh(TreeNode root)
    {
        int count =0;
        while(root!=null){

            count++;

            root=root.right;
        }
        return count;
    }
}