leetcode中等题222.完全二叉树的节点个数

https://leetcode-cn.com/problems/count-complete-tree-nodes/
递归的题目&＃xff0c;左右中的后序遍历思想。

/*** Definition for a binary tree node.* public class TreeNode {* int val;* TreeNode left;* TreeNode right;* TreeNode() {}* TreeNode(int val) { this.val &＃61; val; }* TreeNode(int val, TreeNode left, TreeNode right) {* this.val &＃61; val;* this.left &＃61; left;* this.right &＃61; right;* }* }*/
class Solution {public int countNodes(TreeNode root) {if(root &＃61;&＃61; null) return 0; //确认终止条件int leftNum &＃61; countNodes(root.left); //统计左结点的个数int rightNum &＃61; countNodes(root.right); //统计右节点的个数int count &＃61; leftNum &＃43; rightNum &＃43; 1; //所有节点加起来return count;}
}