222.完全二叉树的节点个数.java

/*
 * @lc app=leetcode.cn id=222 lang=java
 *
 * [222] 完全二叉树的节点个数
 */

// @lc code=start
/**
 * 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;
        return 1 + countNodes(root.left) + countNodes(root.right);
    }
}
// @lc code=end