199. Binary Tree Right Side View

https://leetcode.com/problems/binary-tree-right-side-view/

JavaScript

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
var rightSideView = function(root) {
    if (!root) {
        return []
    }
    const result = []
    let current = [root]
    let next = []
    while (current.length) {
        current.forEach(node => {
            if (node.left) {
                next.push(node.left)
            }
            if (node.right) {
                next.push(node.right)
            }
        })
        result.push(current[current.length - 1].val)
        current = next
        next = []
    }
    return result
};

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 rightSideView(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """
        if not root:
            return []
        result = []
        current, nextRow = [root], []
        while current:
            for node in current:
                if node.left:
                    nextRow.append(node.left)
                if node.right:
                    nextRow.append(node.right)
            result.append(current[-1].val)
            current = nextRow
            nextRow = []
        return result