What is O(log* N)?
What is O(log* N)? I found it online with no description. edit: I know big-Oh, the log* was the question ...
algorithm
A function of a slider value suitable for zooming
I'm using the jquery ui slider for zooming. It's supposed to zoom from 25% to %500, and about half of the range is used for the first %100 of the size. The slider has values from 1 to 100. I need some function that can be used to calculate zooming based on the slider value, e.g. function getZoom(sliderVal) { //return number from 25...
string conversion between UTF-8 representation and unicode representation
How to design an algorithm to convert a UTF-8 string to a unicode string? ...
Collaborative Filtering: Non-Personalized item-to-item similarity
I'm trying to compute item-to-item similarity along the lines of Amazon's "Customers who viewed/purchased X have also viewed/purchased Y and Z". All of the examples and references I've seen are for either computing item similarity for ranked items, for finding user-user similarity, or for finding recommended items based on the current u...
Most efficent way to create all possible combinations of four lists in Python?
I have four different lists. headers, descriptions, short_descriptions and misc. I want to combine these into all the possible ways to print out: header\n description\n short_description\n misc like if i had (i'm skipping short_description and misc in this example for obvious reasons) headers = ['Hello there', 'Hi there!'] descriptio...
Where can I find soft-multiply and divide algorithms?
I'm working on a micro-controller without hardware multiply and divide. I need to cook up software algorithms for these basic operations that are a nice balance of compact size and efficiency. My C compiler port will employ these algos, not the the C developers themselves. My google-fu is so far turning up mostly noise on this topic. ...
How to interchange the position of each of my four ui-elements randomly? - algorithm for the 24 possibilities
I have a program with four different buttons. I want to interchange the position of the buttons randomly. For example: 1 2 3 4 Later: 3 4 1 2 Later: 1 3 2 4 Is there a algorithms for that? The only way I can think is to make a random number from 1 to 24 (24 possibilities) and then code all the possible button postitions. int foo ...
Algorithm for series
A, B, C,…. Z, AA, AB, ….AZ, BA,BB,…. , ZZ,AAA, …., write a function that takes a integer n and returns the string presentation. Can somebody tell me the algorithm to find the nth value in the series? ...
Finding the Reachability Count for all vertices of a DAG
I am trying to find a fast algorithm with modest space requirements to solve the following problem. For each vertex of a DAG find the sum of its in-degree and out-degree in the DAG's transitive closure. Given this DAG: I expect the following result: Vertex # Reacability Count Reachable Vertices in closure 7 5 ...
Variation on Hamiltonian path problems
Thinking about if we modify the definition of Hamiltonian path as we need to go through every edge once,but can pass vertex any times,is there still an algorithm available? How should I modify the original Hamiltonian algorithm to account for this? ...
Are there any "special" image compression algorithms for face cases?
Are there any "special" image compression algorithms for face cases? So i'm creating a canference programm i want to transfer images (or videos) of talking heads thru the internet are there any special algorithms to compress images\videos of talking heads so to make them smaller (like special voice compression algorithms)? ...
Algorithm design: can you provide a solution to the multiple knapsack problem?
I am looking for a pseudo-code solution to what is effectively the Multiple Knapsack Problem (optimisation statement is halfway down the page). I think this problem is NP Complete so the solution doesn't need to be optimal, rather if it is fairly efficient and easily implemented that would be good. The problem is this: I have many wo...
help with number calculation algorithm [hw]
Hi - I'm working on a hw problem that asks me this: given a finite set of numbers, and a target number, find if the set can be used to calculate the target number using basic math operations (add, sub, mult, div) and using each number in the set exactly once (so I need to exhaust the set). This has to be done with recursion. So, for...
algorithm for nth_element
I have recently found out that there exists a method called nth_element in the STL. To quote the description: Nth_element is similar to partial_sort, in that it partially orders a range of elements: it arranges the range [first, last) such that the element pointed to by the iterator nth is the same as the element that wou...
How can we find second maximum from array efficiently?
Is it possible to find the second maximum number from an array of integers by traversing the array only once? As an example, I have a array of five integers from which I want to find second maximum number. Here is an attempt I gave in the interview: #define MIN -1 int main() { int max=MIN,second_max=MIN; int arr[6]={0,1,2,3,4,...
Encoding / Error Correction Challenge
Is it mathematically feasible to encode and initial 4 byte message into 8 bytes and if one of the 8 bytes is completely dropped and another is wrong to reconstruct the initial 4 byte message? There would be no way to retransmit nor would the location of the dropped byte be known. If one uses Reed Solomon error correction with 4 "parity...
How hard is this graph problem?
Hi guys, I have a problem to solve for a social-networks application, and it sounds hard: I'm not sure if its NP-complete or not. It smells like it might be NP-complete, but I don't have a good sense for these things. In any case, an algorithm would be much better news for me. Anyhow, the input is some graph, and what I want to do is ...
How do search engines merge results from an inverted index?
How do search engines merge results from an inverted index? For example, if I searched for the inverted indexes of the words "dog" and "bat", there would be two huge lists of every document which contained one of the two words. I doubt that a search engine walks through these lists, one document at a time, and tries to find matches wit...
Graph colouring algorithm: typical scheduling problem
Hi, I'm training code problems like UvA and I have this one in which I have to, given a set of n exams and k students enrolled in the exams, find whether it is possible to schedule all exams in two time slots. Input Several test cases. Each one starts with a line containing 1 < n < 200 of different examinations to be scheduled. The 2nd...
Algorithm to select a single, random combination of values?
Say I have y distinct values and I want to select x of them at random. What's an efficient algorithm for doing this? I could just call rand() x times, but the performance would be poor if x, y were large. ...