In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning.

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84 views

List comparing techniques for faster performance

I need to cross names from two lists, and find all occurrences of one name in the other. The lists are too big, one have 50k elements and the other 400k. For a small list I would use two foreach ...
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1answer
25 views

Split multiple overlapping intervals to non overlapping intervals

currently I try to build an algorithm to split an array of overlapping intervals to a new array with non overlapping intervals. For example: Array of overlapping intervals: [ {0,7}, {8,12}, ...
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1answer
85 views

Non-fixed-size Fenwick Tree implementation

I'm planning to implement a non-fixed-size Fenwick tree. That is, a Fenwick tree that allows interleaving range queries with adding/removing elements. All implementations and samples I've seen so far ...
0
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5answers
420 views

Fastest way to determine if a value is in a list?

I'm aware there may not be a good solution to this problem. I'm looking for a fast algorithm that determines whether or not a value (let's say an integer) exists in a set of values, however I need the ...
0
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1answer
42 views

Translation algorithm - combinations to indices

I have a deck of 52 poker cards represented as array of int - [0, 1, ... 51]. There are 2.598.960 possible combinations of 5 cards. I can generate all combinations like this: #id #combination ...
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0answers
34 views

scrabble solving with maximum score

I was asked a question You are given a list of characters, a score associated with each character and a dictionary of valid words ( say normal English dictionary ). you have to form a word ...
2
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1answer
236 views

Solving a Sudoku variant with an unknown element

I recently stumbled upon a special Sudoku variant and am now struggling to effectively solve it programatically. Consider the following initial 6x6 grid: The rules The red question mark is ...
-2
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0answers
20 views

generating best fit from 3d datapoints [on hold]

given N datapoints of point(x,y,z) how should I go about generating the best fit line for this dataset? Accuracy is more important than speed as the collection of best fit lines will be precomputed ...
16
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8answers
5k views

Is having trouble with data structures common for beginners? [closed]

I'm taking my second course on Java. We are getting into data structures. I have done an assignment on a linked list, and now a stack. I had a hard time with the linked list. The stack gave me a ...
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1answer
148 views

Calculate Big-O for nested for loops

I found this nested loop to calculate the Big-O notation. for(i=0;i<n;i++) for(j=0;j<i*i;j++) for(k=0;k<j;k++) I got the time complexity for the algorithm with this polynomial ...
2
votes
2answers
784 views

About insertion sort and especially why it's said that copy is much faster than swap?

From Lafore's "Data Structures and Algorithms in Java": (about insertion sort (which uses copy + shift instead of swap (used in bubble and selection sort))) However, a copy isn’t as time-consuming ...
669
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9answers
221k views

Which hashing algorithm is best for uniqueness and speed?

Which hashing algorithm is best for uniqueness and speed? Example (good) uses include hash dictionaries. I know there are things like SHA-256 and such, but these algorithms are designed to be ...
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0answers
23 views

How to do machine learning ensembling [on hold]

I want to know how machine-learning-ensemble is done. how can I ensemble out put of logistic regression and support vector machine.
3
votes
1answer
229 views

Efficient algorithm for Virtual Machine(VM) Consolidation in Cloud

PROBLEM: We have N physical machines(PMs) each with ram Ri, cpu Ci and a set of currently scheduled VMs each with ram requirement ri and ci respectively Moving(Migrating) any VM from one PM to ...
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votes
0answers
22 views

Comparing and adding (math) integers in an array [on hold]

Long time Front-End Dev, new-ish to core programming theories. I am trying to solve a problem, but mentorship to gain better language is needed to progress. Write a method to return the minimum # of ...
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0answers
14 views

Polling more recent / active items more frequently

I'm setting up a service that is meant to query, via a rate-limited API, a number of posts in real-time. Now, some of these posts can be several months old, and they should really only be queried, ...
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2answers
71 views

Average number of comparison for sort algorithms

I need to write different sort algorithms such as bubbleSort insertionSort selectionSort quickSort mergeSort And measure how many average comparison does each one for N number (averaging between ...
2
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3answers
875 views

Algorithmic problem: Picking Cards

The problem below appeared on the last Code Sprint 2 programming competition (it's over already). The base cases are clear, but developing an algorithm that solves all possible cases has been a ...
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2answers
310 views

Just in time prize winning algorithm [closed]

I'm building a contest where you can win prizes by opening boxes. Whatever the box is open, i just send a request to the server to test if the user won something. Since this contest is not a "Register ...
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1answer
105 views

How to selecting Teams with Minimum Difference between Knowledge Levels

For the below challenge from a programming site, I am bit confused. Problem Statement: A Professor of Physics gave projects to the students of his class. The students have to form a team of two for ...
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1answer
139 views

Estimed number of tries

Problem: The Oscar Committee wants to decide which person should get the best actor award among the given N actors.For that they decided to use a random function random_bit() which returns either 0 ...
-1
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1answer
190 views

Optimal movie schedule

Let's say Mr. A goes to cinema and he gets a movie schedule. There are N movies on the program today (1 < N < 50) and for every movie the time of the start and the time of the end are given in ...
7
votes
3answers
768 views

Apple eating problem

Player A and Player B play a game. On the middle of the table there is a pot full of N apples of different weights. Player A starts first and choose an apple and start eating it. Losing no time player ...
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5answers
5k views

Champaign Fountain Puzzle

Empty glasses of water are arranged in the following order: When you pour liquid into the 1st glass if it's full, then the extra liquid would be flown into the glasses 2 and 3 in equal quantities. ...
0
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1answer
682 views

Puzzle solving: Minimum number of steps to achieve a goal

I have been doing some programming contest problems, and I have noticed that many of them involve something along the lines of "get the minimum number of steps necessary to achieve a certain goal". ...
3
votes
5answers
456 views

Which mathematical properties apply to XOR Swap algorithm (and similar bitwise operator algorithms)?

Assume you have two variables a and b, and you need to swap them, and for whatever reason, making a temporary variable for storage is not an option. This is the algorithm in pseudocode a ← a XOR b b ...
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2answers
128 views

Is there a approximate string comparison function which is odd like mathematical functions are odd?

I say odd like a mathematical function, a mathematical function is odd if f(-x) = -f(x) I understand that comparing two strings may seem to have little to do with this, because the arguments cannot ...
5
votes
1answer
275 views

Does anybody recognize this scheduling problem? Is there an algorithm for it?

Consider the following problem: Description: There are n jobs J1...Jn with cycle times C1....Cn. Find a time quanta and a scheduling table considering that: any element of the table contains at ...
2
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0answers
67 views

Asking questions to the user based on results of previous questions

I have to select a question that would help me make me sure the user knows about a given subject. As an example, let's assume the user hasn't answered any question yet. Every question has a scope ...
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3answers
144 views

Does it really need to convert decimal,string, etc to binary?

I'm very new to programming. Just read some articles about algorithm for converting a decimal or string to binary. But,according to what I know, computers hold these data in binary form. So why don't ...
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0answers
41 views

Compare names and the use of Levenshtein's algorithm

I need to cross names from two lists. What is the best away to compare the names? As you may expect, in one list we can have the complete name, on the other just the first and last. Besides that, ...
2
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1answer
71 views

How to count sort comparison

When it is said that this sort has M number of comparisons what does it mean? As an example: procedure bubbleSort( A : list of sortable items ) n = length(A) repeat swapped = false ...
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4answers
269 views

algorithm to extract “possibilities” from a tree

From a given tree, subsequent trees have to be generated. Nodes can be marked as "variant" in the given tree (the example uses an asterisk to mark the node). All possible combinations between the ...
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votes
6answers
1k views

Algorithm to generate N random numbers between A and B which sum up to X

This problem seemed like something which should be solvable with but a few lines of code. Unfortunately, once I actually started to write the thing, I've realized it's not as simple as it sounds. ...
3
votes
2answers
200 views

How to draw rectangles for 2D arrays

I have an 2D boolean array that looks like this: [0][0][0][0][0][0][0][0][0][0] [0][0][0][0][0][0][0][0][0][0] [0][0][0][0][0][0][0][0][0][0] [0][0][0][1][1][1][0][0][0][0] ...
2
votes
2answers
212 views

Dynamic Programming Problem - To find smallest integer number 'x' which contains only digits 1's and 0's such that x mod n = 0

To design an algorithm that will output the smallest integer number 'x' which contains only digits 1's and 0's such that x mod n = 0 and x > 0..... For example: 2 divides 10 3 divides 111 4 ...
0
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1answer
187 views

Turn over cards in minimum number of steps

Imagine you're given an array of cards. Some of them are facing down (0), while some of them are facing up (1). Is it possible for given fixed K to turn all the cards face-up by turning over any K ...
3
votes
1answer
93 views

Merge directed acyclic graphs minimizing number of nodes

I have some DAGs (directed acylic graphs) and I want to merge them in order to minimize the number of nodes (we could say that every node has a cost, while edges are free). These four different DAGs ...
2
votes
0answers
61 views

Can't figure out class scheduling issue? [closed]

"You are a college advisor trying to help students plan their academic careers. You have the list of courses in each major and their prerequisites. Students often want to take their major courses as ...
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0answers
63 views

How do you recognize when topological sort shoudl be used? [closed]

What are the general properties of a programming problem that hint to the necessity of topological sort?
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1answer
214 views

Given a subset of numbers and subset of sums. Match the numbers to sums.(Harder than appears)

I'm not sure what the most efficent solution to this algorithm is. I'm not sure this fits exact cover, and approaching it via exhaustive backtracking seems somewhat inefficient. Any suggestions on how ...
9
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9answers
2k views

Big O Question about an algorithm with (n^2 + n) / 2 growth rate

I'm asking this question because I am confused about one aspect regarding big O notation. I am using the book, Data Structures and Abstractions with Java by Frank Carrano. In the chapter on the ...
0
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0answers
45 views

Efficient all-pairs set intersection on GPU

I have n sets, subsets of a finite universe. I want to calculate the n*n matrix in which the (I, J) entry contains the cardinality of the intersection of set I and set J. n is in the order of 50000. ...
3
votes
2answers
232 views

How to iterate through all permutations of valid links between nodes

Imagine a 2D area, with a number (array) of nodes (or points) defined within it, in arbitrary (but known) positions (integer x,y coordinates), like this: From there I want to be able to, ...
0
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0answers
94 views

What algorithm to convert an integer to unique non-linear string? [closed]

What algorithm that can be used to convert a 32-bit integer to a unique non-linear string? For example: 1 -> DGKJUFD21 2 -> IDFMSOF89 3 -> GDSJH83AS and so on.. This is linear string: 1 ...
2
votes
2answers
401 views

Reduce a list of IPv4 to lowest common CIDR

I have a long list of IP addresses that show some pattern of closeness Example: XX.249.91.16 XX.249.91.21 XX.249.91.32 XX.249.91.160 XX.249.91.165 XX.249.92.15 XX.249.92.25 ...
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votes
0answers
27 views

Rating formula including rating and number of votes [closed]

Is there any other formulas for rating calculation besides IMDB one? I have 10-stars rating TOP-100 chart, and what in that chart that for example entry with rating 9.6 and 56 number of votes would be ...
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votes
1answer
61 views

What do I need to parse sentence for a “simple bot” [closed]

I am developing a chat bot with Node.Js. I am trying to find efficient way to parsing sentence. what do you think about humanity -> ba bla bla. what do you think about cats ->I love cats ...
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0answers
205 views

Karger's algorithm for bin-packing?

I first came across that algorithm as the "Random minimum cut" algorithm. And recently a colleague was trying to pack a big quantity of small textures into one image file. Then it clicked - why not ...
13
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5answers
4k views

What would be the Impact of P=NP? [closed]

I am preparing for a test and I can't find a clear answer on the question: What would be the impact of proving that PTIME=NPTIME. I checked wikipedia and it just mentioned that it would have "profound ...