LeetCode: Binary Tree Right Side View

// https://code.dennyzhang.com/binary-tree-right-side-view
// Basic Ideas: BFS
// Complexity: Time O(n), Space O(h)
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func rightSideView(root *TreeNode) []int {
    res := []int{}
    if root == nil { return res }
    queue := []*TreeNode{root}
    for len(queue) > 0 {
        l := []*TreeNode{}
        for i, node := range queue {
            if i == len(queue)-1 {
                res = append(res, node.Val)
            }
            if node.Left != nil {
                l = append(l, node.Left)
            }
            if node.Right != nil {
                l = append(l, node.Right)
            }
        }
        queue = l
    }
    return res
}

## https://code.dennyzhang.com/binary-tree-right-side-view
## Basic Ideas:
##        Level order traversal. And get the right most for each level
##                1
##              /   \
##             2     3
##            /
##           4
##        return: 1, 3, 4
## Complexity:
##        Time O(k), Space O(k). k is the height of the tree
# 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 root is None:
            return []
        res = []
        queue = []
        queue.append(root)
        while len(queue) != 0:
            length = len(queue)
            for i in xrange(length):
                element = queue[0]
                del queue[0]
                if element.left:
                    queue.append(element.left)
                if element.right:
                    queue.append(element.right)
                # right most element
                if i == length - 1:
                    res.append(element.val)
        return res