Day 51 – Evening Session: DS – Tree Introduction & Terminology – ECET 2026

In Data Structures, Trees are a fundamental topic. ECET 2026 often asks direct questions on terminology, properties, and formulas related to trees. Mastering the basics makes advanced topics like Binary Trees, BST, and AVL easy to learn.

📘 Concept Notes

🌳 What is a Tree?

• A Tree is a non-linear data structure consisting of nodes connected by edges.
• Unlike arrays/linked lists (linear), trees represent hierarchical relationships.
• Example: Family Tree, File System Directory.

⚙️ Basic Terminology of Trees

• Node: Fundamental unit containing data.
• Root: The topmost node of the tree.
• Parent: A node that has children.
• Child: A node directly connected below another node.
• Leaf (Terminal Node): A node with no children.
• Internal Node: A node having at least one child.
• Sibling: Nodes with the same parent.
• Degree of Node: Number of children a node has.
• Degree of Tree: Maximum degree of any node.
• Level of Node: Distance (in edges) from the root.
• Height of Node: Longest path from that node to a leaf.
• Height of Tree: Height of the root node.

🔋 Important Formulas

1. Maximum number of nodes at level k:

Maximum number of nodes in a tree of height h:

For a binary tree:

• If = total nodes, then maximum height = .
• Minimum height = .

Relationship:
(in a full binary tree).

📐 Example

Consider a binary tree with 7 nodes arranged in 3 levels:

        A (root)
       /   \
      B     C
     / \   / \
    D   E F   G

        A (root)
       /   \
      B     C
     / \   / \
    D   E F   G

• Root = A
• Leaves = D, E, F, G
• Internal Nodes = B, C
• Height = 2 (edges from root to leaf)
• Degree of root = 2

🔟 10 Expected MCQs – ECET 2026

Q1. A tree is a:
A) Linear data structure
B) Non-linear data structure
C) Both
D) None

Q2. In a tree, the topmost node is called:
A) Leaf
B) Root
C) Parent
D) Child

Q3. A node with no children is called:
A) Internal Node
B) Root
C) Leaf
D) Sibling

Q4. The number of children of a node is known as:
A) Degree
B) Height
C) Level
D) Depth

Q5. Maximum number of nodes at level k = ?
A)
B)
C)
D)

Q6. Maximum number of nodes in a binary tree of height h is:
A)
B)
C)
D)

Q7. In a full binary tree, number of leaf nodes = ?
A) Internal nodes
B) Degree-2 nodes + 1
C) Degree-1 nodes
D) Root

Q8. Which of the following is NOT true about trees?
A) A tree has exactly one root.
B) Every child has exactly one parent.
C) Trees may contain cycles.
D) A tree with n nodes has n−1 edges.

Q9. Height of a tree with only 1 node is:
A) 0
B) 1
C) 2
D) Undefined

Q10. If a binary tree has 15 nodes, its maximum height is:
A) 15
B) 14
C) 10
D) 7

✅ Answer Key

🧠 Explanations

• Q1 → B: Trees are hierarchical, hence non-linear.
• Q2 → B: Topmost node = Root.
• Q3 → C: Nodes with no children are leaves.
• Q4 → A: Degree = number of children.
• Q5 → B: Formula = .
• Q6 → B: Formula = .
• Q7 → B: In full binary tree, leaves = degree-2 nodes + 1.
• Q8 → C: Trees never contain cycles.
• Q9 → A: Height of single node tree = 0.
• Q10 → B: Max height = N−1 = 14.

🎯 Why Practice Matters

• Tree terminology questions are frequently repeated in ECET exams.
• Easy scoring because formulas are straightforward.
• Strong basics help in advanced DS topics like traversal, BST, AVL, Heap.

📲 Join Our ECET Prep Community on WhatsApp

👉 Join WhatsApp Group – Click Here