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mediumDSA

How do you get the right-side view of a binary tree?

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01

Understand the problem

Explain right-side view.

treesbfs
02

Attempt it yourself

Sketch your approach before reading the solution — that's what interviews test.

Nudge consolestandby

Stuck? Beam a request up — the console returns a conceptual nudge that guides your logic without spoiling the implementation.

03

Study the solution

Do a level-order BFS and take the last node of each level, which is what you'd see from the right. Alternatively a DFS visiting right-first and recording the first node seen at each new depth. O(n).

Solution ready — 2 min read

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04

Read the code

Level-order BFS, last per level
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from collections import deque

class TreeNode:
    def __init__(self, val, left=None, right=None):
        self.val, self.left, self.right = val, left, right

def right_side_view(root):
    if not root:
        return []
    view, q = [], deque([root])
    while q:
        n = len(q)
        for i in range(n):
            node = q.popleft()
            if i == n - 1:              # last node of this level
                view.append(node.val)
            if node.left: q.append(node.left)
            if node.right: q.append(node.right)
    return view


# --- demo ---
root = TreeNode(1, TreeNode(2, None, TreeNode(5)), TreeNode(3, None, TreeNode(4)))
print(right_side_view(root))   # [1, 3, 4]
05

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