222. Count Complete Tree Nodes

https://leetcode.com/problems/count-complete-tree-nodes/

JavaScript

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var countNodes = function(root) {
    if (!root) {
        return 0
    }
    return countNodes(root.left) + countNodes(root.right) + 1
};

JavaScript

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var countNodes = function(root) {
    if (!root) {
        return 0
    }
    let count = 0
    let nodes = [root]
    while (nodes.length) {
        count += 1
        const node = nodes.shift()
        if (node.left) {
            nodes.push(node.left)
        }
        if (node.right) {
            nodes.push(node.right)
        }
    }
    return count
};

Python

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None


class Solution(object):

    def countNodes(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        if not root:
            return 0
        return self.countNodes(root.left) + self.countNodes(root.right) + 1

Go

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func countNodes(root *TreeNode) int {
    if root == nil {
        return 0
    }
    return countNodes(root.Left) + countNodes(root.Right) + 1
}