【2022初春】【LeetCode】【树】222. 完全二叉树的节点个数

这道题学的是，求二叉树的深度，节点个数，在完全二叉树的基础上，怎么简化深度
以及完全二叉树求节点个数的优化
求二叉树的深度

private int countLevel(TreeNode root){
    if(root == null){
        return 0;
    }
    return Math.max(countLevel(root.left),countLevel(root.right)) + 1;
}

求二叉树的节点个数

public int countNodes(TreeNode root) {
    if (root == null){
        return 0;
    }
    return countNodes(root.left) + countNodes(root.right) + 1;
}

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int countNodes(TreeNode root) {
        if(root==null) return 0;
        int lefth = dfs(root.left);
        int righth = dfs(root.right);
        if(lefth==righth) return (int)Math.pow(2,lefth) + countNodes(root.right);
        else return (int)Math.pow(2,righth) + countNodes(root.left);

    }
    int dfs(TreeNode root){
        int high = 0;
        if(root==null) return 0;
        while(root!=null){
            high++;
            root = root.left;
        }
        return high;
    }
}