# Questions tagged [algorithms]

An algorithm is a sequence of well-defined steps that defines an abstract solution to a problem. Use this tag when your issue is related to design and analysis of algorithms.

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### In-place algorithm for interleaving an array

You are given an array of $2n$ elements $$a_1, a_2, \dots, a_n, b_1, b_2, \dots b_n$$ The task is to interleave the array, using an in-place algorithm such that the resulting array looks like ...
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### Do you get DFS if you change the queue to a stack in a BFS implementation?

Here is the standard pseudocode for breadth first search: ...
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### Graph searching: Breadth-first vs. depth-first

When searching graphs, there are two easy algorithms: breadth-first and depth-first (Usually done by adding all adjactent graph nodes to a queue (breadth-first) or stack (depth-first)). Now, are ...
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### How is the loop invariant obtained in this square root bound finding algorithm?

Originally on math.SE but unanswered there. Consider the following algorithm. ...
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### Hash tables versus binary trees

When implementing a dictionary ('I want to look up customer data by their customer IDs'), the typical data structures used are hash tables and binary search trees. I know for instance that the C++ STL ...
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### How to determine likely connections in a social network?

I am curious in determining an approach to tackling a "suggested friends" algorithm. Facebook has a feature in which it will recommended individuals to you which it thinks you may be acquainted with. ...
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### Analyzing a modified version of the card-game "War"

A simple game usually played by children, the game of War is played by two people using a standard deck of 52 playing cards. Initially, the deck is shuffled and all cards are dealt two the two players,...
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### Identifying events related to dates in a paragraph

Is there an algorithmic approach to identify that dates given in a paragraph correlate to particular events (phrases) in the paragraph? Example, consider the following paragraph: In June 1970, the ...
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### Implementing the GSAT algorithm - How to select which literal to flip?

The GSAT algorithm is, for the most part, straight forward: You get a formula in conjunctive normal form and flip the literals of the clauses until you find a solution that satisfies the formula or ...
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### Why polynomial time is called "efficient"?

Why in computer science any complexity which is at most polynomial is considered efficient? For any practical application(a), algorithms with complexity $n^{\log n}$ are way faster than algorithms ...
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### A Case Distinction on Dynamic Programming: Example Needed!

I have been working on dynamic programming for some time. The canonical way to evaluate a dynamic programming recursion is by creating a table of all necessary values and filling it row by row. See ...
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### The time complexity of finding the diameter of a graph

What is the time complexity of finding the diameter of a graph $G=(V,E)$? ${O}(|V|^2)$ ${O}(|V|^2+|V| \cdot |E|)$ ${O}(|V|^2\cdot |E|)$ ${O}(|V|\cdot |E|^2)$ The diameter of a ...
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### How to come up with the runtime of algorithms? [duplicate]

I've not gone much deep into CS. So, please forgive me if the question is not good or out of scope for this site. I've seen in many sites and books, the big-O notations like $O(n)$ which tell the ...
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### Subset sum, pseudo-polynomial time dynamic programming solution?

I found the P vs NP problem some time ago and I have recently worked on the subset sum problem. I have read Wikipedia article on the Subset Sum problem as well as the question Subset Sum Algorithm I ...
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### Is there a difference between top-down and bottom-up dynamic programming?

Is there a fundamental difference between top-down and bottom-up dynamic programming? In particular, is there a problem which can be solved bottom-up but not top-down? Or is the bottom-up approach ...
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