# Questions tagged [intuition]

Questions that ask for help building intuition for formal or complex concepts.

38 questions
1answer
115 views

### Why don't integer multiplication algorithms use lookup tables?

It seems to me that we can use lookup tables for multiplication of two integers of size $\log(n)/2$, and that the number of entries for each table of these numbers should be $O(n)$. Now, multiplying ...
0answers
41 views

### Intuition behind balancing of link/cut data structure

My question concerns link/cut tree structure after an access operation. I am assuming an implementation with splay trees. As far as I can tell, once you access a node v and splay it to the root, it no ...
1answer
49 views

### What is the simplest/smallest subset an OOP language like C#/JavaScript that is Turing-complete?

This question is not meant to be too theoretical or nitpicky. I have experience programming, so I'm trying to get a better understanding of what it takes to get Turing-completeness by using my ...
0answers
92 views

### Edmond's Blossom algorithm (Maximum Matching) explanation

I asked this question on Math Stackexchange but it didn't get much attention, so I am asking it here. Edmond's Blossom algorithm (Wikipedia), or simply the blossom algorithm, is a popular graph ...
1answer
489 views

### Intuition behind straight-line programs

Wikipedia defines straight-line programs in the following manner: In mathematics, more specifically in computational algebra[disambiguation needed], a straight-line program (SLP) for a finite group ...
3answers
610 views

### To what extent is my interpretation of computable numbers correct?

Interpretation: Consider the comic strip below, where a person tries to prevent a robot from dismembering them by asking the robot to compute $\pi$ - the robot quickly produces an algorithm to ...
1answer
61 views

### Of monotone formulas and same ones satisfying certain properties

There is the following theoretical computer science, namely: For a particular monotone formula $M$ of size $n$, there's an equivalent formula of depth $\text{O}(\text{ln}\,n)$. (I am reading the ...
0answers
217 views

### What is the intuition behind balancing in AVL trees?

I am not sure that my question is clear from the first sight. But I will try to explain what I mean. For now, I am learning balancing the trees on the example of AVL trees. We know that to balance ...
0answers
133 views

### Intuitive Explanation on Converting BNF Grammar to LR(1)

Consider the following BNF Grammar G: ...
1answer
319 views

### Elimination rule for the equality type aka J axiom

I'm implementing a interpreter for lambda calculus, and now I want to add the equality type. The introduction rule for it is easy, but the elimination rule is rather obscure for me. I found this ...
2answers
138 views

### Is the following intuition valid for understanding $k$-wise independent hash functions?

I really enjoy reading up on algorithms and data structures and in the course of doing so often come across ones that rely on $k$-wise independent families of hash functions. I'm perfectly comfortable ...
3answers
3k views

### What does it mean for a problem to be both NP hard and coNP hard

I have a faint notion of what NP hard is (that a problem is legit difficult 3 SAT for example). I have forgotten what coNP hard, and Wikipedia tells me that the complement of coNP hard is NP hard......
1answer
129 views

### An intuitive explanation for LR grammars?

With LL grammars, there seems to be a very intuitive explanation, in terms of first and follow tables.( The first letter/s encountered in a particular state, can only mean a particular rule). With LR ...
5answers
590 views

### Google's Deep Dreamer

I was just wondering on a more technical side, if anyone could explain what Google does to create these amazing images from it's deep dream system. Could anyone explain to me in a step by step way, ...
7answers
5k views

### Is there a more intuitive proof of the halting problem's undecidability than diagonalization?

I understand the proof of the undecidability of the halting problem (given for example in Papadimitriou's textbook), based on diagonalization. While the proof is convincing (I understand each step of ...
2answers
607 views

### Why can Multilayer neural networks solve non-linear problems

I understand what a multilayer neural network is, but what about them allows them to solve non-linear problems unlike perceptrons? Is it the fact that they can extend to any number of outputs/hidden ...
1answer
402 views

### Intuition behind the max-flow min-cut theorem

What is the intuition behind the max-flow min-cut theorem? I know that the min-cut is the dual of max-flow when formulated as a linear program, but the result seems artificial to me.
2answers
459 views

### Given the “programs as proofs” isomorphism, how do we know that the program isn't lying?

I've been studying constructive type theory (CTT) and one of the things that I'm not clear on is the proof part: Proving the correctness of a program in a form of a proof that's nothing but the ...
1answer
247 views

### How does selection sort sort?

I've found the following algorithm for selection sort on the internet. ...
2answers
321 views

### What do we gain by having “dependent types”?

I thought I understood dependent typing (DT) properly, but the answer to this question: https://cstheory.stackexchange.com/questions/30651/why-was-there-a-need-for-martin-l%C3%B6f-to-create-...
2answers
7k views

### Why do we believe that PSPACE ≠ EXPTIME?

I'm having trouble intuitively understanding why PSPACE is generally believed to be different from EXPTIME. If PSPACE is the set of problems solvable in space polynomial in the input size $f(n)$, ...
2answers
2k views

### How can I use the NP complexity Venn diagram to quickly see which class of NP problem can be poly reducible to another class?

I'm so bad at solving the problem of the type: "If $A$ is an NP-complete problem, $B$ is reducible to $A$, then $B$ is..." That I have to come here and ask these silly questions each and every ...
1answer
557 views

### Visualization of Lamport's three-dimensional “space-time diagram” with introduced “tick lines”

In the third page (the third paragraph in the right column) of the paper "Time, Clocks, and the Ordering of Events in a Distributed System" by Leslie Lamport, it says that The reader may find it ...
1answer
163 views

### Learning, understanding and using algorithms [closed]

I am a 2nd year computer science student. We all have subjects about Data Structures, Theories, more more theories we all know that i have a subject this semester Design Analysis of Algorithms. So ...
2answers
1k views

### Why is automatically labeling data in unsupervised learning hard?

I currently studying machine learning and pattern recognition area. Today, my professor said implementing an unsupervised system that automatically labels data is difficult. Why is that? I think if I ...
5answers
228 views

### Real life description for (~A->A)->A

It can be shown that the logical preposition [ :- (~A->A)->A ] is a theorem (always true). I want to know if anybody knows a real life description for the preposition above? I mean an expression in ...
2answers
160 views

### What does it mean to multiply or divide polynomials?

What does it mean to multiply or divide polynomials? I have used them so many times, in error correcting codes, cryptography, etc. but it was never clear to me what would be a graphical ...
5answers
9k views

### How to tell if a language is recognizable, co-recognizable or decidable?

If you have a language L, without doing any proofs, is there a way to tell if it's recognizable or co-recognizable or decidable? Basically any hints or tricks that can be used to tell. Or maybe the ...
7answers
10k views

### What are the characteristics of a $\Theta(n \log n)$ time complexity algorithm?

Sometimes it's easy to identify the time complexity of an algorithm my examining it carefully. Algorithms with two nested loops of $N$ are obviously $N^2$. Algorithms that explore all the possible ...
3answers
992 views

### Intuition for convolution in image processing

I have read many documents about convolution in image processing, and most of them say about its formula, some additional parameters. No one explains the intuition and real meaning behind doing ...
3answers
327 views

### Why larger input sizes imply harder instances?

Below, assume we're working with an infinite-tape Turing machine. When explaining the notion of time complexity to someone, and why it is measured relative to the input size of an instance, I ...
4answers
3k views

### Is it intuitive to see that finding a Hamiltonian path is not in P while finding Euler path is?

I am not sure I see it. From what I understand, edges and vertices are complements for each other and it is quite surprising that this difference exists. Is there a good / quick / easy way to see ...
3answers
1k views

### How to feel intuitively that a language is regular

Given a language $L= \{a^n b^n c^n\}$, how can I say directly, without looking at production rules, that this language is not regular? I could use pumping lemma but some guys are saying just looking ...
1answer
220 views

### Turing Recognisable => enumerable

I get the proof of going from an enumerator to a Turing Machine (keep running enumerator and see if it matches input) but I don't see how the other way works. According to my notes and the book (...
2answers
8k views

### Rule of thumb to know if a problem could be NP-complete

This question was inspired by a comment on StackOverflow. Apart from knowing NP-complete problems of the Garey Johnson book, and many others; is there a rule of thumb to know if a problem looks like ...
4answers
4k views

### Why is $L= \{ 0^n 1^n | n \geq 1 \}$ not regular language?

I'm looking for intuition about when a language is regular and when it is not. For example, consider: $$L = \{ 0^n 1^n \mid n \geq 1 \} = \{ 01, 0011, 000111, \ldots \}$$ which is not a regular ...
8answers
4k views

### Algorithmic intuition for logarithmic complexity

I believe I have a reasonable grasp of complexities like $\mathcal{O}(1)$, $\Theta(n)$ and $\Theta(n^2)$. In terms of a list, $\mathcal{O}(1)$ is a constant lookup, so it's just getting the head of ...
4answers
481 views

### Strategies for becoming unstuck in understanding TCS

I am a graduate student taking a course in theory of computation and I have serious trouble producing content once I'm asked to. I'm able to follow the textbook (Introduction to the Theory of ...