1
What is the index of the first element in an array?
- A
0
- B
1
- C
-1
- D
Depends on language
Show AnswerHide Answer
✓ A. 0
📊 130+ Questions • Updated 2026
Data Structures
Multiple Choice Questions
Master Data Structures with 130+ curated MCQs covering arrays, linked lists, stacks, queues, trees, graphs, hashing, sorting, and searching. Perfect for exams, interviews, and placements.
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📝Data Structures MCQs(131 questions)
2
Which of the following operations is efficient on an array?
- A
Access by index
- B
Insertion at the beginning
- C
Deletion from the middle
- D
Searching unsorted
Show AnswerHide Answer
✓ A. Access by index
3
What is a multidimensional array?
- A
An array of arrays
- B
A one-dimensional array
- C
A dynamic array
- D
A sorted array
Show AnswerHide Answer
✓ A. An array of arrays
4
What is the time complexity of searching an element in an unsorted array?
- A
O(1)
- B
O(log n)
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ C. O(n)
5
What is the time complexity of inserting an element at the end of a dynamic array?
- A
O(1) amortized
- B
O(n)
- C
O(log n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(1) amortized
6
Which of the following is true about a circular array?
- A
It uses a fixed-size buffer
- B
It can be implemented using modulo
- C
Both A and B
- D
It is a linked list
Show AnswerHide Answer
✓ C. Both A and B
7
What is a linked list?
- A
A linear data structure where elements are stored at contiguous memory locations
- B
A linear data structure where elements are stored at non-contiguous memory locations
- C
A data structure that uses hashing
- D
A data structure that uses trees
Show AnswerHide Answer
✓ B. A linear data structure where elements are stored at non-contiguous memory locations
8
What is the time complexity of inserting a node at the beginning of a singly linked list?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(1)
9
What is the time complexity of searching for an element in a singly linked list?
- A
O(1)
- B
O(log n)
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ C. O(n)
10
What is a doubly linked list?
- A
Each node has two pointers: next and prev
- B
Each node has only one pointer
- C
It is a circular list
- D
It is a sorted list
Show AnswerHide Answer
✓ A. Each node has two pointers: next and prev
11
What is the advantage of a doubly linked list over a singly linked list?
- A
Can traverse in both directions
- B
Uses less memory
- C
Faster insertion
- D
Easier to implement
Show AnswerHide Answer
✓ A. Can traverse in both directions
12
What is a circular linked list?
- A
The last node points to the first node
- B
The list has no end
- C
Both A and B
- D
It uses circular array
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✓ C. Both A and B
13
What is a stack?
- A
A data structure that follows LIFO (Last In First Out)
- B
A data structure that follows FIFO (First In First Out)
- C
A data structure that stores elements in sorted order
- D
A data structure that uses hashing
Show AnswerHide Answer
✓ A. A data structure that follows LIFO (Last In First Out)
14
Which operation is used to add an element to a stack?
- A
push
- B
pop
- C
peek
- D
enqueue
Show AnswerHide Answer
✓ A. push
15
Which operation is used to remove an element from a stack?
- A
pop
- B
push
- C
top
- D
dequeue
Show AnswerHide Answer
✓ A. pop
16
What is the time complexity of push and pop operations in a stack implemented using an array?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(1)
17
Which of the following is a common application of stacks?
- A
Expression evaluation
- B
Function call management
- C
Undo operations
- D
All of the above
Show AnswerHide Answer
✓ D. All of the above
18
What is the meaning of stack overflow?
- A
Trying to push onto a full stack
- B
Trying to pop from an empty stack
- C
Stack memory is corrupted
- D
Stack pointer is lost
Show AnswerHide Answer
✓ A. Trying to push onto a full stack
19
What is a queue?
- A
A data structure that follows FIFO (First In First Out)
- B
A data structure that follows LIFO
- C
A data structure that sorts elements
- D
A data structure for priority
Show AnswerHide Answer
✓ A. A data structure that follows FIFO (First In First Out)
20
Which operation is used to add an element to a queue?
- A
enqueue
- B
dequeue
- C
push
- D
pop
Show AnswerHide Answer
✓ A. enqueue
21
Which operation is used to remove an element from a queue?
- A
dequeue
- B
enqueue
- C
front
- D
rear
Show AnswerHide Answer
✓ A. dequeue
22
What is a circular queue?
- A
A queue where the last position wraps around to the first
- B
A queue implemented using a circular linked list
- C
A queue with no end
- D
A queue that uses priority
Show AnswerHide Answer
✓ A. A queue where the last position wraps around to the first
23
What is a priority queue?
- A
Each element has a priority; higher priority elements are dequeued first
- B
Elements are enqueued in priority order
- C
It is implemented using a heap
- D
All of the above
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✓ D. All of the above
24
What is the time complexity of enqueue and dequeue in a simple queue implemented with an array?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(1)
25
What is a tree data structure?
- A
A hierarchical data structure with a root and child nodes
- B
A linear data structure
- C
A cyclic data structure
- D
A data structure with no ordering
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✓ A. A hierarchical data structure with a root and child nodes
26
What is a binary tree?
- A
Each node has at most two children
- B
Each node has exactly two children
- C
Each node has any number of children
- D
It is a tree with only one node
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✓ A. Each node has at most two children
27
What is a binary search tree (BST)?
- A
Left child < parent < right child
- B
Left child > parent > right child
- C
All nodes are equal
- D
No ordering is maintained
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✓ A. Left child < parent < right child
28
What is the time complexity of searching in a balanced BST?
- A
O(1)
- B
O(log n)
- C
O(n)
- D
O(n^2)
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✓ B. O(log n)
29
What is a tree traversal?
- A
Visiting each node in the tree in a specific order
- B
Adding nodes to the tree
- C
Removing nodes from the tree
- D
Finding the height of the tree
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✓ A. Visiting each node in the tree in a specific order
30
What is the difference between a full binary tree and a complete binary tree?
- A
Full: every node has 0 or 2 children; Complete: all levels filled except possibly last
- B
Full: all levels filled; Complete: every node has 2 children
- C
They are the same
- D
Full is a subset of complete
Show AnswerHide Answer
✓ A. Full: every node has 0 or 2 children; Complete: all levels filled except possibly last
31
What is a heap data structure?
- A
A specialized tree-based structure that satisfies the heap property
- B
A queue with priorities
- C
A binary tree with no ordering
- D
A linked list
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✓ A. A specialized tree-based structure that satisfies the heap property
32
What is a min-heap?
- A
Parent is less than or equal to children
- B
Parent is greater than or equal to children
- C
Children are less than parent
- D
No ordering property
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✓ A. Parent is less than or equal to children
33
What is a max-heap?
- A
Parent is greater than or equal to children
- B
Parent is less than or equal to children
- C
Children are greater than parent
- D
No ordering
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✓ A. Parent is greater than or equal to children
34
What is the time complexity to find the maximum element in a max-heap?
- A
O(1)
- B
O(log n)
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(1) (it is the root)
35
What is the time complexity to insert an element into a heap?
- A
O(1)
- B
O(log n)
- C
O(n)
- D
O(n^2)
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✓ B. O(log n)
36
Which data structure is commonly used to implement a priority queue?
- A
Heap
- B
Array
- C
Linked List
- D
Stack
Show AnswerHide Answer
✓ A. Heap
37
What is a graph?
- A
A data structure consisting of vertices and edges
- B
A tree with no cycles
- C
A linear data structure
- D
A hashing structure
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✓ A. A data structure consisting of vertices and edges
38
What is a directed graph?
- A
Edges have a direction
- B
Edges have no direction
- C
All vertices are connected
- D
It is a tree
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✓ A. Edges have a direction
39
What is the degree of a vertex in an undirected graph?
- A
The number of edges incident to it
- B
The number of vertices connected to it
- C
The number of outgoing edges
- D
The number of incoming edges
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✓ A. The number of edges incident to it
40
What is the time complexity of Breadth-First Search (BFS) on a graph with V vertices and E edges?
- A
O(V + E)
- B
O(V^2)
- C
O(E^2)
- D
O(V * E)
Show AnswerHide Answer
✓ A. O(V + E)
41
What is the time complexity of Depth-First Search (DFS) on a graph with V vertices and E edges?
- A
O(V + E)
- B
O(V^2)
- C
O(E^2)
- D
O(V * E)
Show AnswerHide Answer
✓ A. O(V + E)
42
Which algorithm is used to find the shortest path in an unweighted graph?
- A
BFS
- B
DFS
- C
Dijkstra
- D
Bellman-Ford
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✓ A. BFS
43
What is hashing?
- A
A technique to map data to a fixed-size value
- B
A technique to sort data
- C
A technique to link nodes
- D
A technique to traverse trees
Show AnswerHide Answer
✓ A. A technique to map data to a fixed-size value
44
What is a hash table?
- A
A data structure that uses a hash function to map keys to buckets
- B
A sorted array
- C
A linked list
- D
A tree
Show AnswerHide Answer
✓ A. A data structure that uses a hash function to map keys to buckets
45
What is a collision in hashing?
- A
Two different keys map to the same index
- B
Two same keys map to different indices
- C
The hash table is full
- D
The hash function is not defined
Show AnswerHide Answer
✓ A. Two different keys map to the same index
46
What is the load factor of a hash table?
- A
Number of elements / table size
- B
Table size / number of elements
- C
Number of collisions
- D
Hash function output
Show AnswerHide Answer
✓ A. Number of elements / table size
47
Which collision resolution technique uses linked lists?
- A
Chaining
- B
Open addressing
- C
Double hashing
- D
Linear probing
Show AnswerHide Answer
✓ A. Chaining
48
What is the average time complexity for search, insert, and delete in a well-designed hash table?
- A
O(1)
- B
O(log n)
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(1)
49
What is the time complexity of Bubble Sort in the worst case?
- A
O(n)
- B
O(n log n)
- C
O(n^2)
- D
O(log n)
Show AnswerHide Answer
✓ C. O(n^2)
50
What is the time complexity of Merge Sort in all cases?
- A
O(n log n)
- B
O(n^2)
- C
O(n)
- D
O(log n)
Show AnswerHide Answer
✓ A. O(n log n)
51
Which sorting algorithm has the best average-case time complexity?
- A
Quick Sort
- B
Bubble Sort
- C
Selection Sort
- D
Insertion Sort
Show AnswerHide Answer
✓ A. Quick Sort (O(n log n) average)
52
What is the time complexity of Quick Sort in the worst case?
- A
O(n log n)
- B
O(n^2)
- C
O(n)
- D
O(log n)
Show AnswerHide Answer
✓ B. O(n^2)
53
Which sorting algorithm is stable?
- A
Merge Sort
- B
Quick Sort
- C
Heap Sort
- D
Selection Sort
Show AnswerHide Answer
✓ A. Merge Sort
54
Which sorting algorithm is in-place?
- A
Quick Sort
- B
Merge Sort
- C
Radix Sort
- D
Counting Sort
Show AnswerHide Answer
✓ A. Quick Sort (can be in-place)
55
What is the time complexity of linear search?
- A
O(1)
- B
O(log n)
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ C. O(n)
56
What is the time complexity of binary search?
- A
O(1)
- B
O(log n)
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ B. O(log n)
57
What is the prerequisite for binary search?
- A
The array must be sorted
- B
The array must be unsorted
- C
The array must contain unique elements
- D
The array must be circular
Show AnswerHide Answer
✓ A. The array must be sorted
58
What is the time complexity of interpolation search?
- A
O(1)
- B
O(log log n) average
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ B. O(log log n) average
59
What is the worst-case time complexity of interpolation search?
- A
O(n)
- B
O(log n)
- C
O(1)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(n)
60
Which search algorithm works on the principle of divide and conquer?
- A
Binary Search
- B
Linear Search
- C
Jump Search
- D
Exponential Search
Show AnswerHide Answer
✓ A. Binary Search
61
What is the result of rotating an array by one position?
- A
The first element moves to the last
- B
The last element moves to the first
- C
All elements shift right
- D
All elements shift left
Show AnswerHide Answer
✓ A. The first element moves to the last (left rotation)
62
What is the advantage of a circular linked list over a singly linked list?
- A
Traversal can start from any node
- B
Uses less memory
- C
Faster insertion
- D
Easier to implement
Show AnswerHide Answer
✓ A. Traversal can start from any node
63
What is the output of the following operations: push(5), push(10), pop(), push(15), pop(), pop()?
- A
10, 15, 5
- B
15, 10, 5
- C
5, 10, 15
- D
Error
Show AnswerHide Answer
✓ A. 10, 15, 5 (pop returns 10, then 15, then 5)
64
What is the output of the following queue operations: enqueue(1), enqueue(2), dequeue(), enqueue(3), dequeue(), dequeue()?
- A
1, 2, 3
- B
2, 3, 1
- C
1, 3, 2
- D
3, 2, 1
Show AnswerHide Answer
✓ A. 1, 2, 3 (dequeue returns 1, then 2, then 3)
65
What is the height of a tree with a single node?
- A
0
- B
1
- C
2
- D
Undefined
Show AnswerHide Answer
✓ A. 0 (depending on definition, sometimes 1)
66
What is the time complexity to build a heap from an array of n elements?
- A
O(n)
- B
O(n log n)
- C
O(n^2)
- D
O(log n)
Show AnswerHide Answer
✓ A. O(n) (heapify)
67
What is a spanning tree?
- A
A subgraph that includes all vertices and is a tree
- B
A subgraph with minimum edges
- C
A complete graph
- D
A graph with no cycles
Show AnswerHide Answer
✓ A. A subgraph that includes all vertices and is a tree
68
What is double hashing?
- A
Using two hash functions to resolve collisions
- B
Using two hash tables
- C
Hashing twice
- D
Hash function with two parameters
Show AnswerHide Answer
✓ A. Using two hash functions to resolve collisions
69
What is the time complexity of Counting Sort?
- A
O(n + k)
- B
O(n log n)
- C
O(n^2)
- D
O(k log n)
Show AnswerHide Answer
✓ A. O(n + k) where k is the range
70
What is the time complexity of Jump Search?
- A
O(√n)
- B
O(log n)
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(√n)
71
What is the difference between an array and a linked list?
- A
Array is static; linked list is dynamic
- B
Array uses contiguous memory; linked list uses non-contiguous
- C
Both A and B
- D
They are the same
Show AnswerHide Answer
✓ C. Both A and B
72
What is the time complexity to delete a node given only a pointer to it in a singly linked list?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
Show AnswerHide Answer
✓ B. O(n) because you need to find the previous node
73
What is the meaning of stack underflow?
- A
Trying to pop from an empty stack
- B
Trying to push onto a full stack
- C
Stack memory is corrupted
- D
Stack pointer is lost
Show AnswerHide Answer
✓ A. Trying to pop from an empty stack
74
What is a deque?
- A
A double-ended queue
- B
A queue with priority
- C
A circular queue
- D
A stack
Show AnswerHide Answer
✓ A. A double-ended queue
75
What is an AVL tree?
- A
A self-balancing BST
- B
A tree with all nodes at same depth
- C
A tree with no rotation
- D
A tree with left and right subtrees of equal height
Show AnswerHide Answer
✓ A. A self-balancing BST
76
What is the time complexity to delete the root from a heap?
- A
O(log n)
- B
O(1)
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(log n)
77
What is a weighted graph?
- A
Edges have weights or costs
- B
Vertices have weights
- C
Graph has cycles
- D
Graph is directed
Show AnswerHide Answer
✓ A. Edges have weights or costs
78
What is the difference between separate chaining and open addressing?
- A
Chaining uses linked lists; open addressing probes
- B
Open addressing uses linked lists; chaining probes
- C
Both are the same
- D
Chaining is for arrays; open addressing for trees
Show AnswerHide Answer
✓ A. Chaining uses linked lists; open addressing probes
79
What is the time complexity of Heap Sort?
- A
O(n log n)
- B
O(n^2)
- C
O(n)
- D
O(log n)
Show AnswerHide Answer
✓ A. O(n log n) in all cases
80
What is the time complexity of Ternary Search?
- A
O(log n) base 3
- B
O(log n) base 2
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(log n) base 3
81
What is the time complexity of inserting an element at the beginning of an array?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
Show AnswerHide Answer
✓ B. O(n) because shifting elements
82
What is the time complexity of inserting a node at the end of a singly linked list with a tail pointer?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(1)
83
Which data structure is used for recursion?
- A
Stack
- B
Queue
- C
Heap
- D
Array
Show AnswerHide Answer
✓ A. Stack
84
What is the time complexity of checking if a queue is empty?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(1)
85
What is a trie?
- A
A tree used for efficient retrieval of keys
- B
A binary tree
- C
A heap
- D
A graph
Show AnswerHide Answer
✓ A. A tree used for efficient retrieval of keys
86
What is the time complexity to find the minimum element in a min-heap?
- A
O(1)
- B
O(log n)
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(1) (at root)
87
What is Dijkstra's algorithm used for?
- A
Shortest path in weighted graphs
- B
Shortest path in unweighted graphs
- C
Minimum spanning tree
- D
Topological sorting
Show AnswerHide Answer
✓ A. Shortest path in weighted graphs
88
What is a perfect hash function?
- A
Injective mapping with no collisions
- B
A hash function with many collisions
- C
A hash function with no load factor
- D
A hash function that maps all keys to same value
Show AnswerHide Answer
✓ A. Injective mapping with no collisions
89
What is the time complexity of Insertion Sort in the worst case?
- A
O(n)
- B
O(n log n)
- C
O(n^2)
- D
O(log n)
Show AnswerHide Answer
✓ C. O(n^2)
90
What is the time complexity of Exponential Search?
- A
O(log n)
- B
O(n)
- C
O(n^2)
- D
O(1)
Show AnswerHide Answer
✓ A. O(log n) (for binary search part)
91
What is the difference between a static array and a dynamic array?
- A
Static array has fixed size; dynamic array can grow
- B
Static array uses heap; dynamic uses stack
- C
Both are the same
- D
Static array is faster
Show AnswerHide Answer
✓ A. Static array has fixed size; dynamic array can grow
92
What is the time complexity to find the length of a singly linked list?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
Show AnswerHide Answer
✓ B. O(n)
93
Which of the following is true about a stack implemented using a linked list?
- A
Push and pop are O(1)
- B
Push and pop are O(n)
- C
Memory is contiguous
- D
It can't be implemented
Show AnswerHide Answer
✓ A. Push and pop are O(1)
94
What is the difference between a simple queue and a circular queue?
- A
Circular queue reuses space; simple queue doesn't
- B
Simple queue is faster
- C
Both are the same
- D
Circular queue uses linked list
Show AnswerHide Answer
✓ A. Circular queue reuses space; simple queue doesn't
95
What is the time complexity to search for a value in a BST in the worst case?
- A
O(n)
- B
O(log n)
- C
O(1)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(n) (if unbalanced)
96
What is the time complexity to find the maximum element in a max-heap?
- A
O(1)
- B
O(log n)
- C
O(n)
- D
O(n^2)
Show AnswerHide Answer
✓ A. O(1)
97
What is a cycle in a graph?
- A
A path that starts and ends at the same vertex
- B
A path with no repeated vertices
- C
A path with no edges
- D
A path with all vertices distinct
Show AnswerHide Answer
✓ A. A path that starts and ends at the same vertex
98
What is a hash collision?
- A
Two different keys hash to same value
- B
Two same keys hash to different values
- C
Hash table is full
- D
Hash function is broken
Show AnswerHide Answer
✓ A. Two different keys hash to same value
99
What is the time complexity of Radix Sort?
- A
O(nk)
- B
O(n log n)
- C
O(n^2)
- D
O(k)
Show AnswerHide Answer
✓ A. O(nk) where k is number of digits
100
What is the worst-case time complexity of Fibonacci Search?
- A
O(log n)
- B
O(n)
- C
O(n^2)
- D
O(1)
Show AnswerHide Answer
✓ A. O(log n)
101
What is a sparse array?
- A
An array with mostly zero or default values
- B
An array with all elements filled
- C
An array of objects
- D
A two-dimensional array
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✓ A. An array with mostly zero or default values
102
What is a skip list?
- A
A linked list with multiple levels for fast search
- B
A list with no nodes
- C
A circular linked list
- D
A doubly linked list
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✓ A. A linked list with multiple levels for fast search
103
What is the time complexity of evaluating a postfix expression using a stack?
- A
O(n)
- B
O(n^2)
- C
O(log n)
- D
O(1)
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✓ A. O(n)
104
What is the time complexity of enqueue and dequeue in a linked list-based queue?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
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✓ A. O(1) with head and tail pointers
105
What is a B-tree?
- A
A balanced tree with multiple children per node
- B
A binary tree
- C
A heap
- D
A graph
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✓ A. A balanced tree with multiple children per node
106
What is the time complexity to increase the priority of an element in a heap?
- A
O(log n)
- B
O(1)
- C
O(n)
- D
O(n^2)
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✓ A. O(log n) (up-heapify)
107
What is the time complexity of Prim's algorithm for minimum spanning tree?
- A
O(E log V)
- B
O(V^2)
- C
O(E + V log V)
- D
Both A and C depending on implementation
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✓ D. Both A and C depending on implementation
108
What is the worst-case time complexity of search in a hash table using chaining?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
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✓ B. O(n) (if all keys collide)
109
Which sorting algorithm is based on the divide and conquer paradigm?
- A
Merge Sort
- B
Bubble Sort
- C
Selection Sort
- D
Insertion Sort
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✓ A. Merge Sort
110
What is the time complexity of Linear Search in the average case?
- A
O(n)
- B
O(n/2)
- C
O(1)
- D
O(n^2)
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✓ A. O(n)
111
What is a jagged array?
- A
An array of arrays where each inner array can have different length
- B
A 2D array with equal rows and columns
- C
A sorted array
- D
A dynamic array
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✓ A. An array of arrays where each inner array can have different length
112
What is the time complexity to reverse a singly linked list?
- A
O(n)
- B
O(1)
- C
O(log n)
- D
O(n^2)
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✓ A. O(n)
113
What is the output of the following: push(2), push(3), pop(), push(5), pop(), pop()?
- A
3, 5, 2
- B
2, 5, 3
- C
5, 3, 2
- D
2, 3, 5
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✓ A. 3, 5, 2
114
What is the time complexity of checking the front element of a queue?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
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✓ A. O(1)
115
What is the time complexity to insert an element into a balanced BST?
- A
O(log n)
- B
O(n)
- C
O(1)
- D
O(n^2)
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✓ A. O(log n)
116
What is the time complexity to delete an arbitrary element from a heap?
- A
O(log n)
- B
O(n)
- C
O(1)
- D
O(n^2)
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✓ A. O(log n) after finding its position, but finding requires O(n) unless you have a handle
117
What is the time complexity of DFS using an adjacency list?
- A
O(V + E)
- B
O(V^2)
- C
O(E^2)
- D
O(V * E)
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✓ A. O(V + E)
118
What is the time complexity of insertion in a hash table with open addressing?
- A
O(1) average
- B
O(n) worst case
- C
O(log n)
- D
Both A and B
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✓ D. Both A and B
119
What is the time complexity of Quick Sort in the average case?
- A
O(n log n)
- B
O(n^2)
- C
O(n)
- D
O(log n)
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✓ A. O(n log n)
120
What is the time complexity of Binary Search in the worst case?
- A
O(log n)
- B
O(n)
- C
O(1)
- D
O(n^2)
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✓ A. O(log n)
121
What is the time complexity of finding the maximum element in an unsorted array?
- A
O(n)
- B
O(log n)
- C
O(1)
- D
O(n^2)
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✓ A. O(n)
122
What is the time complexity to insert a node after a given node in a singly linked list?
- A
O(1)
- B
O(n)
- C
O(log n)
- D
O(n^2)
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✓ A. O(1)
123
What is the use of a stack in compilers?
- A
Syntax analysis and expression evaluation
- B
Code generation
- C
Memory allocation
- D
All of the above
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✓ A. Syntax analysis and expression evaluation
124
What is a priority queue implemented using?
- A
Heap
- B
Array
- C
Linked List
- D
Stack
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✓ A. Heap
125
What is the time complexity to find the height of a binary tree?
- A
O(n)
- B
O(log n)
- C
O(1)
- D
O(n^2)
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✓ A. O(n) (visit all nodes)
126
What is the space complexity of a heap?
- A
O(n)
- B
O(log n)
- C
O(1)
- D
O(n^2)
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✓ A. O(n)
127
What is a bipartite graph?
- A
Vertices can be divided into two sets with no edges within a set
- B
A graph with edges only in one direction
- C
A complete graph
- D
A graph with cycles
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✓ A. Vertices can be divided into two sets with no edges within a set
128
What is the purpose of a hash function?
- A
To map keys to indices in a hash table
- B
To sort data
- C
To link nodes
- D
To balance trees
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✓ A. To map keys to indices in a hash table
129
What is the time complexity of Shell Sort in the worst case?
- A
O(n^2)
- B
O(n log n)
- C
O(n)
- D
O(log n)
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✓ A. O(n^2)
130
What is the time complexity of Sentinel Linear Search?
- A
O(n)
- B
O(log n)
- C
O(1)
- D
O(n^2)
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✓ A. O(n) (but faster in practice)
131
What is the time complexity of accessing an element in an array by index?
- A
O(1)
- B
O(log n)
- C
O(n)
- D
O(n^2)
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✓ A. O(1)
❓Frequently Asked Questions
What is a data structure?
A data structure is a way of organizing and storing data in a computer so that it can be accessed and modified efficiently. Common data structures include arrays, linked lists, stacks, queues, trees, graphs, and hash tables.
What is the difference between an array and a linked list?
Arrays store elements in contiguous memory locations, allowing O(1) random access but insertion/deletion is O(n). Linked lists store elements in non-contiguous memory with pointers, allowing O(1) insertion/deletion at known positions but O(n) access time.
What is the Stack data structure and its applications?
Stack follows LIFO (Last In First Out) principle. Applications include function call management, expression evaluation, undo/redo operations, parsing, and backtracking (e.g., recursion).
What is the Queue data structure and its applications?
Queue follows FIFO (First In First Out) principle. Applications include scheduling (CPU, disk), breadth-first search, print spooling, and handling asynchronous data (e.g., producer-consumer).
What is a Binary Search Tree (BST) and its advantages?
A BST is a binary tree where left child < parent < right child. It supports search, insert, delete in O(log n) average time if balanced. It provides ordered data and efficient searching.
What is the difference between a heap and a BST?
A heap is a complete binary tree used for priority queues; it satisfies heap property (max-heap or min-heap). BST maintains sorted order and supports search, insert, delete. Heap supports efficient max/min extraction and insertion.
What is hashing and why is it used?
Hashing is a technique to map data (keys) to fixed-size values (hash codes) using a hash function. Hash tables provide O(1) average time for search, insert, and delete. Used in dictionaries, caches, and databases.
What are the common sorting algorithms and their complexities?
Common algorithms: Bubble Sort (O(n^2)), Insertion Sort (O(n^2)), Selection Sort (O(n^2)), Merge Sort (O(n log n)), Quick Sort (O(n log n) average, O(n^2) worst), Heap Sort (O(n log n)). Choice depends on data size and stability requirements.