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Problem Detail: If a decision problem A belongs to the polynomial complexity class P, must there be at least one YES instance and one NO instance of the problem? I know that in the definition of a Turing machine an accept Read More …

Problem Detail: This is a follow-up question of this one. In a previous question about exotic state machines, Alex ten Brink and Raphael addressed the computational capabilities of a peculiar kind of state machine: min-heap automata. They were able to show Read More …

Problem Detail: Given an English sentence, I am looking for a programmatic way to tell whether the sentence is written in passive voice. Currently, I just check if there is a was or were inside the sentence. If yes, then the Read More …

Problem Detail: If an algorithm runs in exponential time with exponential input then we say it runs in polynomial time ? Why ? Doesn’t the algorithm run in exponential time anyway ? How the input size affects ? Thanks. Asked By Read More …

Problem Detail: I’ve been trying to make a CFG, and npda/pda for this language (to construct an npda for accepting the language): L(M)={ww:w∈{a,b}∗,|w| is even}. i had already solved the reverse of the language (like this): L′={wwR:w∈{a,b}∗}, Please check this snapshot Read More …

Problem Detail: Someone recently claimed that there’s an adversarial input for randomized quicksort; he referenced this paper. This defies my intuition because there are results that say that randomized quicksort runs in $O(n log n)$ time with high probability. (See, for Read More …

Problem Detail: I am stuck on the following question If L is regular show that even(L) is also regular where even(L) = {even(w) : w ∈ L} w is a string in L even(w) is the string obtained by extracting from Read More …

Problem Detail: it’s my understanding that when you XOR something, the result is the sum of the two numbers mod 2. why then does 4^2 = 6 and not 0? 4+2=6, 6%2 doesn’t equal 6. I must be missing something about Read More …

Problem Detail: 3-PARTITION is strongly NP-complete, i.e. it remains NP-complete even if the input is given in unary. I’m searching two or three examples of (possibly well-known) non-numeric problems that have been proved to be NP-complete using a reduction from 3-PARTITION Read More …