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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 21

Catalan number C(n) counts?
Distinct BSTs with n keys
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Which sorting is best for only 0s, 1s, 2s?
Dutch National Flag (3-way partition)
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Building a heap from n elements time complexity?
O(n)
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What is a sparse graph?
Few edges relative to vertices
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2-3 tree is?
B-tree of order 3 (each internal node 2 or 3 children)
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Python list.pop(0) vs list.pop() difference?
pop(0) removes front O(n); pop() removes end O(1)
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BTreeSearch returns if key not found?
NIL (NULL)
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mid in mergesort([5,9,10,1,66])?
2
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Result of quicksort([56,25,93,15,31,44])?
[15,25,31,44,56,93]
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Binary search on [12,24,32,39,45,50,54] for 45 returns?
4
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dict.items() returns?
All key-value pairs as tuples
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Python set vs list membership check?
List O(n); Set O(1) average
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Tuple vs list in Python?
Tuple immutable and hashable; List mutable
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Ford-Fulkerson algorithm solves:
Maximum flow in a network
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Longest Increasing Subsequence (LIS) of {3,10,2,1,20} has length:
3
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Matrix Chain Multiplication uses which technique?
Dynamic Programming
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Edit distance (Levenshtein distance) between "kitten" and "sitting" is:
3
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Coin change problem (minimum coins) uses:
Dynamic Programming for general case
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KMP (Knuth-Morris-Pratt) algorithm efficiently solves:
String pattern matching in O(n+m)
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The failure function in KMP is used to:
Skip unnecessary comparisons by tracking longest proper prefix-suffix
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Rabin-Karp algorithm uses:
Rolling hash for efficient multi-pattern search
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Data Structures and Algorithms → Sorting Algorithms 7

Heap sort total time complexity?
O(n log n)
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Quick sort space complexity?
O(log n) average call stack
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Merge step of merge sort for two halves of size n/2?
O(n)
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Selection sort best case time complexity?
O(n²)
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Number of levels in merge sort for n=8?
3
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In bubble sort after one pass on [9,16,6,26,0], result?
[9,6,16,0,26]
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Selection sort result on [5,3,7,1,9,6]?
[1,3,5,6,7,9]
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Data Structures and Algorithms → Linked List 1

Best sorting for linked list with nearly sorted data?
Insertion sort
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Data Structures and Algorithms → Binary Search Tree 1

Maximum height of BST with n nodes?
n-1 (skewed tree)
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Data Structures and Algorithms → Trees 2

In B-tree, keys within each node stored in?
Increasing order
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B-tree maximum height formula for n keys, order t?
log_t((n+1)/2)
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Data Structures and Algorithms → Queue 2

deque.appendleft() equivalent to?
Insert at front of queue
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Queue remaining after enqueue(A,B,C),dequeue(),enqueue(D),dequeue()?
C,D
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Data Structures and Algorithms → Stack 3

Stack output after push(Amar,Akbar,Anthony,Ram,Iqbal),pop()?
Iqbal
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Final stack after push(1),push(2),pop(),push(3),push(4),pop(),pop()?
[1]
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Stack remaining after push(5),push(3),pop(),push(7),push(1),pop(),pop()?
[5]
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Data Structures and Algorithms → Graphs 1

Kruskal algorithm finds MST by:
Sorting all edges and adding non-cycle-forming edges
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Data Structures and Algorithms → Dynamic Programming 2

Which problem is solved by dynamic programming with O(nW) complexity?
0/1 Knapsack problem
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Longest Common Subsequence (LCS) of "ABCBDAB" and "BDCABA" has length:
4
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