## Top new questions this week:

### Explaining the difference between computer science and computer literacy

What is a good metaphor or example to explain to an English major the difference between classical computer science and "being good with using MS-Windows" computer science computer programming …

terminology education

### Why choose D* over Dijkstra?

I understand the basis of A* as being a derivative of Dijkstra, however, I recently found out about D*. From Wikipedia, I can understand the algorithm. What I do not understand is why I would use D* …

algorithms graphs search-algorithms efficiency

### Finite representations and programming languages Countably inifite

I'm going over some of the pre-requisite math regarding Automata theory, and finite representations. I read the following: If ∑ is a finite alphabet the set of all strings over the alphabet (∑*) is …

discrete-mathematics

### Regarding the Turing Machine

I am a high school student in the twelfth grade. I study high-level programming, and a little bit of basic computer science. I have recently started to understand what a Turing Machine is. I wanted …

turing-machines

### Lamport's Byzantine Generals Algorithm

I've stumbled at the first OralMessage algorithm in Lamport, et al's paper. I've searched the web and there are dozens of sites, restating in exactly the same terms and examples, which isn't helping …

distributed-systems fault-tolerance

### How does binary addition work?

I find binary confusing. I have watched minecraft redstone videos on binary adders, real binary adders, diagrams, etc and yet I have not learned much at all. How does electrons flowing through wires …

logic binary-arithmetic

### Mapping intuitionistic logic to the modal logic S4

In his famous Semantical Analysis of Intuitionistic Logic, S. Kripke speaks of the "well-known mappings of intuitionistic logic into the modal system S4". I'm not sure which mappings Kripke means. One …

reference-request logic modal

## Greatest hits from previous weeks:

### What is a the fastest sorting algorithm for an array of integers?

I have come across many sorting algorithms during my high school studies. However, I never know which is the fastest (for a random array of integers). So my questions are: Which is the fastest …

algorithms time-complexity optimization sorting

### Knapsack problem -- NP-complete despite dynamic programming solution?

Knapsack problems are easily solved by dynamic programming. Dynamic programming runs in polynomial time; that is why we do it, right? I have read it is actually an NP-complete problem, though, which …

complexity-theory np-complete dynamic-programming

### PDA structure for the language $w_1 \ne w^R \mid w, w_1 \in \{a,b\}^*$

Consider the language: $L = \{ww_1 : w, w_1 \in \{a,b\}^* w^R \ne w_1\}$ The task is to find a PDA to represent the language. The book I'm using is Formal Languages and Automata by Linz, and the …

formal-languages pushdown-automata

### Type systems understanding problems

I'm not sure if this is the correct place to ask this kind of a question, but here goes: I'm doing my own reading of the Principles of Program Analysis book, and i'm having trouble understanding some …

type-theory