Topic: Data Structures – Trees – Top 15 Interview Questions with Answers
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### 1. What is a tree data structure?
A hierarchical structure with nodes connected by edges, having a root node and child nodes with no cycles.
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### 2. What is the difference between binary tree and binary search tree (BST)?
A binary tree allows up to two children per node; BST maintains order where left child < node < right child.
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### 3. What are the types of binary trees?
Full, perfect, complete, skewed (left/right), and balanced binary trees.
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### 4. Explain tree traversal methods.
Inorder (LNR), Preorder (NLR), Postorder (LRN), and Level Order (BFS).
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### 5. What is a balanced tree? Why is it important?
A tree where the height difference between left and right subtrees is minimal to ensure O(log n) operations.
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### 6. What is an AVL tree?
A self-balancing BST maintaining balance factor (-1, 0, 1) with rotations to balance after insert/delete.
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### 7. What are rotations in AVL trees?
Operations (Left, Right, Left-Right, Right-Left) used to rebalance the tree after insertion or deletion.
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### 8. What is a Red-Black Tree?
A balanced BST with red/black nodes ensuring balance via color rules, offering O(log n) operations.
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### 9. How does a Trie work?
A tree structure used for storing strings, where nodes represent characters, allowing fast prefix searches.
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### 10. What is the height of a binary tree?
The number of edges on the longest path from root to a leaf node.
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### 11. How do you find the lowest common ancestor (LCA) of two nodes?
By traversing from root, checking if nodes lie in different subtrees, or by storing parent pointers.
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### 12. What is the difference between DFS and BFS on trees?
DFS explores as far as possible along branches; BFS explores neighbors level by level.
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### 13. How do you detect if a binary tree is a BST?
Check if inorder traversal yields a sorted sequence or verify node values within valid ranges recursively.
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### 14. What are leaf nodes?
Nodes with no children.
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### 15. How do you calculate the number of nodes in a complete binary tree?
Using the formula: number\_of\_nodes = 2^(height + 1) - 1 (if perfect), else traverse and count.
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### Exercise
Write functions for inorder, preorder, postorder traversals, check if tree is BST, and find LCA of two nodes.
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#DSA #Trees #InterviewQuestions #BinaryTrees #Python #Algorithms
---
### 1. What is a tree data structure?
A hierarchical structure with nodes connected by edges, having a root node and child nodes with no cycles.
---
### 2. What is the difference between binary tree and binary search tree (BST)?
A binary tree allows up to two children per node; BST maintains order where left child < node < right child.
---
### 3. What are the types of binary trees?
Full, perfect, complete, skewed (left/right), and balanced binary trees.
---
### 4. Explain tree traversal methods.
Inorder (LNR), Preorder (NLR), Postorder (LRN), and Level Order (BFS).
---
### 5. What is a balanced tree? Why is it important?
A tree where the height difference between left and right subtrees is minimal to ensure O(log n) operations.
---
### 6. What is an AVL tree?
A self-balancing BST maintaining balance factor (-1, 0, 1) with rotations to balance after insert/delete.
---
### 7. What are rotations in AVL trees?
Operations (Left, Right, Left-Right, Right-Left) used to rebalance the tree after insertion or deletion.
---
### 8. What is a Red-Black Tree?
A balanced BST with red/black nodes ensuring balance via color rules, offering O(log n) operations.
---
### 9. How does a Trie work?
A tree structure used for storing strings, where nodes represent characters, allowing fast prefix searches.
---
### 10. What is the height of a binary tree?
The number of edges on the longest path from root to a leaf node.
---
### 11. How do you find the lowest common ancestor (LCA) of two nodes?
By traversing from root, checking if nodes lie in different subtrees, or by storing parent pointers.
---
### 12. What is the difference between DFS and BFS on trees?
DFS explores as far as possible along branches; BFS explores neighbors level by level.
---
### 13. How do you detect if a binary tree is a BST?
Check if inorder traversal yields a sorted sequence or verify node values within valid ranges recursively.
---
### 14. What are leaf nodes?
Nodes with no children.
---
### 15. How do you calculate the number of nodes in a complete binary tree?
Using the formula: number\_of\_nodes = 2^(height + 1) - 1 (if perfect), else traverse and count.
---
### Exercise
Write functions for inorder, preorder, postorder traversals, check if tree is BST, and find LCA of two nodes.
---
#DSA #Trees #InterviewQuestions #BinaryTrees #Python #Algorithms
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