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GK One-Line Question & Answer

15541+ short questions with short answers, covering every category and sub-category on the site — no long articles to scroll through. Good for a fast recap before an exam, or a few minutes of daily practice.

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Data Structures and Algorithms → Introduction to DSA 27

Naive recursive Fibonacci time complexity?
O(2^n) exponential
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Time complexity of Python list append()?
O(1) amortized
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Hash collision is?
Two keys hash to same index
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Chaining in hash tables?
Colliding elements in linked list at same bucket
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Open addressing in hash tables?
Finding next available slot in array
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Load factor of hash table?
Elements/Buckets
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Heap data structure?
Complete binary tree with heap property
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Extract minimum from min-heap time complexity?
O(log n)
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Python module for heap operations?
heapq
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Time complexity of accessing element at index i in array?
O(1)
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Min-heap property?
Parent <= children
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Amortized time complexity?
Average cost per operation over sequence
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Python set membership check time complexity?
O(1) average
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Trie (prefix tree) is?
Tree storing strings, each node=character
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Trie search time complexity?
O(L) where L=word length
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Union-Find find() with path compression?
O(α(n)) ≈ O(1) amortized
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Red-Black tree is?
Self-balancing BST with red/black coloring rules
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LRU Cache best implementation?
Doubly Linked List + Hash Map
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Segment tree used for?
Range queries (sum/min/max) with efficient updates
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Fenwick tree (BIT) is?
Efficient prefix sum queries and point updates in O(log n)
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KMP algorithm used for?
String pattern matching in O(n+m)
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Timsort is?
Hybrid of merge sort and insertion sort
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Number of distinct BSTs with 3 keys?
5
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Comparison-based sorting lower bound?
O(n log n)
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All AVL operations time complexity?
O(log n)
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B+ tree used in databases because?
Faster range queries via linked leaves
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Timsort best case time complexity?
O(n) for already sorted
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Data Structures and Algorithms → Dynamic Programming 1

Fibonacci with memoization time complexity?
O(n)
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Data Structures and Algorithms → Recursion 2

Tower of Hanoi with n disks requires how many moves?
2^n - 1
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sys.setrecursionlimit() is used to?
Set maximum recursion depth
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Data Structures and Algorithms → Graphs 1

Tree vs graph difference?
Tree is connected acyclic graph with n-1 edges for n nodes
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Data Structures and Algorithms → Linked List 1

Time complexity of finding middle node of linked list?
O(n)
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Data Structures and Algorithms → Arrays 1

Insertion at beginning of array of n elements?
O(n)
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Data Structures and Algorithms → Trees 6

After inserting 1,2,3 into AVL tree, which rotation?
RR
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AVL tree LR rotation applied when?
New node in right of left child
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B-tree insertion always occurs at?
Leaf level
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Full B-tree node during insertion: operation performed?
Split at median, push median up
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B-tree of order 5: minimum keys in non-root node?
2
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Minimum degree t=2 B-tree: root has at least?
2 children
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Data Structures and Algorithms → Stack 1

Stack implementation using linked list advantage?
Never overflows (unless memory exhausted)
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