Right view of a binary tree

right_view_of_binary_tree.py

class Node:
    def __init__(self, value=None, left=None, right=None):
        self.value = value
        self.left = left
        self.right = right

    def __repr__(self):
        return str(self.value)


def right_view(tree):
    viewing_depth = 0
    ans = []

    queue = [(tree, 0)]
    while len(queue) > 0:
        node, depth = queue.pop(0)

        if node is not None:
            if depth == viewing_depth:
                ans.append(node.value)
                viewing_depth += 1

            queue.append((node.right, depth + 1))
            queue.append((node.left, depth + 1))

    return ans

def right_view(tree):
    ans = []
    width = 1
    queue = [tree]

    while len(queue) > 0:
        level, queue = queue[:width], queue[width:]

        width = 0
        seen = False
        for node in level:
            if node is not None:
                queue.append(node.right)
                queue.append(node.left)
                width += 2

                if not seen:
                    ans.append(node.value)
                    seen = True

    return ans


t1 = None

t2 = Node(
    1,
    left=Node(
        2,
        right=Node(
            5,
            left=Node(4),
        ),
    ),
    right=Node(
        3,
        left=Node(6),
    ),
)

t3 = Node(
    1,
    left=Node(
        2,
        left=Node(4),
    ),
    right=Node(
        3,
        left=Node(5),
        right=Node(
            6,
            left=Node(7)
        ),
    ),
)

assert right_view(t1) == []
assert right_view(t2) == [1, 3, 6, 4]
assert right_view(t3) == [1, 3, 6, 7]