Q&A for students, researchers and practitioners of computer science

258 Why is quicksort better than other sorting algorithms in practice? 2012-03-06T19:11:07.127

212 What is the definition of $P$, $NP$, $NP$-complete and $NP$-hard? 2013-02-06T20:38:08.297

168 Why is writing down mathematical proofs more fault-proof than writing computer code? 2017-12-11T13:11:12.130

157 How can a language whose compiler is written in C ever be faster than C? 2015-08-22T14:13:48.210

136 Is there a system behind the magic of algorithm analysis? 2014-04-09T12:59:52.003

125 How can it be decidable whether $\pi$ has some sequence of digits? 2012-03-14T13:19:52.857

124 Why, really, is the Halting Problem so important? 2014-11-08T16:44:58.327

117 Why are there so many programming languages? 2012-03-17T06:00:44.033

113 Why can I look at a graph and immediately find the closest point to another point, but it takes me O(n) time through programming? 2014-03-17T06:05:56.817

105 Is Category Theory useful for learning functional programming? 2012-08-03T17:52:13.360

93 Why hasn't there been an encryption algorithm that is based on the known NP-Hard problems? 2012-03-14T08:02:26.627

90 How to convert finite automata to regular expressions? 2012-05-23T08:19:27.003

89 How not to solve P=NP? 2012-05-17T01:24:29.327

86 How/when is calculus used in Computer Science? 2016-04-05T00:21:33.837

85 What are the reasons to learn different algorithms / data structures serving the same purpose? 2016-02-17T06:13:26.403

82 How to prove that a language is not context-free? 2012-03-12T23:57:46.817

78 How does one know which notation of time complexity analysis to use? 2012-03-07T01:42:10.933

78 BIT: What is the intuition behind a binary indexed tree and how was it thought about? 2013-03-15T17:56:58.113

78 How to fool the "try some test cases" heuristic: Algorithms that appear correct, but are actually incorrect 2014-08-28T20:51:43.760

76 Why is the unit of image size not Pixel²? 2018-02-13T14:11:44.177

73 Why are some programming languages "faster" or "slower" than others? 2017-03-24T07:05:51.820

71 What does the "Lambda" in "Lambda calculus" stand for? 2016-04-13T12:58:53.817

70 How to prove that a language is not regular? 2012-04-04T10:30:32.163

69 Graph searching: Breadth-first vs. depth-first 2012-03-13T10:05:58.093

69 Solving or approximating recurrence relations for sequences of numbers 2012-07-17T18:31:38.607

68 How can we assume that basic operations on numbers take constant time? 2012-05-03T00:06:31.453

67 Why is deep learning hyped despite bad VC dimension? 2017-05-13T12:43:43.370

66 Is there any concrete relation between Gödel's incompleteness theorem, the halting problem and universal Turing machines? 2012-03-15T16:43:28.693

65 What's the difference between a binary search tree and a binary heap? 2014-06-20T04:43:44.160

64 (When) is hash table lookup O(1)? 2012-03-12T19:01:07.577

64 What is the novelty in MapReduce? 2012-08-03T14:04:19.350

64 What properties of a programming language make compilation impossible? 2014-09-02T10:19:14.790

63 Quicksort Partitioning: Hoare vs. Lomuto 2013-04-21T08:02:32.013

63 How can I explain to my parents that I study programming languages? 2016-05-01T15:01:57.167

60 Are there any problems that get easier as they increase in size? 2016-01-02T04:11:39.003

60 Why do we not combine random number generators? 2016-05-20T01:32:54.023

60 Why don't compilers automatically insert deallocations? 2017-01-12T19:38:33.750

59 Can a dynamic language like Ruby/Python reach C/C++ like performance? 2012-03-28T01:27:42.453

58 Why is addition as fast as bit-wise operations in modern processors? 2017-05-23T23:44:43.203

57 Language theoretic comparison of LL and LR grammars 2012-03-07T00:32:31.947

57 What is coinduction? 2012-03-19T17:34:08.127

56 Algorithmic intuition for logarithmic complexity 2012-03-21T05:51:41.653

55 In-place algorithm for interleaving an array 2012-03-13T20:16:32.067

54 What would be the real-world implications of a constructive $P=NP$ proof? 2014-12-29T18:59:34.997

53 How do computers keep track of time? 2016-03-25T17:33:09.713

53 Is zero allowed as an edge's weight, in a weighted graph? 2016-07-28T10:10:39.077

53 If everyone believes P ≠ NP, why is everyone sceptical of proof attempts for P ≠ NP? 2017-10-19T00:17:15.187

52 Formal program verification in practice 2013-08-17T01:51:39.910

52 Does a byte contain 8 bits, or 9? 2016-12-20T16:44:03.907

52 How is this sorting algorithm Θ(n³) and not Θ(n²), worst-case? 2017-01-18T03:37:42.240