Unanswered Questions
639 questions with no upvoted or accepted answers
14
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What can be proven regarding the differences in power between unary ECMAScript regex functions and primitive recursive functions?
In 2014, inspired by Regex Golf, I started exploring, along with a mathematician going by the name teukon, what could be done in the unary domain in ECMAScript regex that went significantly beyond ...
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12
votes
1
answer
5k
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Finding the longest repeating subsequence
Given a string $s$, I would like to find the longest repeating (at least twice) subsequence. That is, I would like to find a string $w$ which is a subsequence (doesn't have to be a contiguous) of $s$ ...
- 280k
9
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784
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How can the shortest traveling salesman tour be found in $O(2^n poly(n))$ time and less than exponential space?
I'm stuck on problem 9.4 from The Nature of Computation which reads:
Dynamic Salesman. A naive search algorithm for TSP takes $O(n!)$ time to check all tours. Use dynamic programming to reduce this ...
- 1,058
9
votes
1
answer
853
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Turing Machine-Like Formalism for The Actor Model
Turing machines have a formal symbol alphabet, state and transition-rules based description of how a computation is done.
The Actor Model is sometimes mentioned as a more powerful computational-...
CommunityBot
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8
votes
0
answers
159
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Make a tag system simulate a finite automaton?
Tag systems are Turing-complete. I was wondering if there is any easy way to create tag systems that simulate finite automata. So create tag systems that recognize languages, e.g. by having at the end ...
- 73.1k
8
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0
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647
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Chained operations on sequences with two operators
Given a binary expresion tree, with addition and multiplication operations, how can we optimize it's evaluation?
Can we learn from matrix chain multiplication? A generalization of matrix chain ...
CommunityBot
- 1
6
votes
0
answers
97
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Scheduling tasks on a graph with assistance
This is a follow-up to a question that I recently posted here: Completing tasks on a graph. In that question, I posted the following:
Consider a graph $G = (V, E)$, where $V = \{0, 1, 2, \ldots, n\}$. ...
CommunityBot
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6
votes
0
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543
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What could we say about that conjecture that yields P != NP?
Let $F$ be the set of all Boolean formulae.
We say that a Boolean formula $\varphi$ is positive (=monotone) if
$\forall \alpha\in F,i\leq n$, if $\alpha\wedge\neg x_i\models\varphi$, then $\alpha\...
- 231
6
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0
answers
108
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Calculating with regexes
We use a regex engine (say, PCRE) that allows grouping subexpressions with parentheses and recalling the value they match in the search / replace expressions (backreferences, denoted by \i for ...
- 323
6
votes
1
answer
124
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A dynamic program to decide whether the solution is in a given range
In the subset sum problem, the input is a list of positive integers $x_1,\ldots,x_n$ and an integer $T$, and the goal is to decide whether there is a subset of sum exactly $T$.
The problem can be ...
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5
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0
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437
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Where is simply typed lambda calculus on the Chomsky hiererchy?
The functions definable in untyped lambda calculus are the computable functions, for which it is in turn possible to define equivalences to the concepts of Turing machines, recursive enumerability and ...
- 815
5
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0
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55
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The evolution of the term "recursive" from Goedel to Church to present day
I'm currently studying some of the history of computation / computability, in the early days known as recursion theory.
I see Goedel's definition of recursive functions seems significant in his paper,...
- 317
5
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0
answers
457
views
Count Wildcard Parenthesizations of a String
Let $\Sigma = \{ (, ), ? \}$ be an alphabet. For a given string $s \in \Sigma^*$, we denote by $f(s)$ the number of ways to replace each symbol $?$ either with $($ or with $)$ such that $s$ is ...
- 73.1k
5
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0
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180
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Sequence Alignment with Skips
In my thesis I am working on a problem connected with sequence alignment, in particular, I deal with the Dynamic Time Warping (DTW) algorithm (see this for more), which is used to evaluate the ...
5
votes
1
answer
1k
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2D version of LeetCode house robber problem
The house robber problem of leetcode can be described as followed :
A robber enters a colony of houses numbered from 1 to n. Every house has a number printed on the top of it. That number is the ...
CommunityBot
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