mediumDSA

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

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

**Intuition.** Standing to the right of the tree, you see exactly the **last node of each level**. A level-order BFS processes the tree one level at a time, so capturing the last node dequeued per level gives the right-side view directly. last node of each level (green) is what the right eye sees <line x1="300" y1="106" x2="330" y2="142" stroke="currentColor" strok

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Explain right-side view.

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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]

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