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0
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3answers
377 views

How to create single integer index value based on two integers where first is unlimited?

I have table data containing an integer value X ranging from 1.... unknown, and an integer value Y ranging from 1..9 The data need to be presented in order 'X then Y'. For one visual component I can ...
-1
votes
5answers
2k views

Reverse subarray of an array with O(1)

I have an idea how to implement sub array reverse with O(1), not including precalculation such as reading the input. I will have many reverse operations, and I can't use the trivial solution of O(N). ...
0
votes
2answers
2k views

efficient way to count number of swaps in insertion sort

I am browsing some online coding challenge online and got struck somewhere . Objective of program is to find maximum number of swaps required in sorting an array via insertion sort in efficient time ...
1
vote
1answer
139 views

Heuristic for consistiently ordering points in a a plane

I have rectangular regions in a plane. I want to consistently order them in a human-friendly way that a typical y-x sort won't work for. Basically I want (0,0), (1,0), and (0,1) to sort the same as ...
0
votes
1answer
834 views

Use ruby's array sort() method, or add items in correct place with a binary lookup?

If I am loading a whole load of items (un-ordered words from a file or something) would it be more efficient to load them all to a Ruby array, and then use the built in sort! method or to do a binary ...
0
votes
1answer
440 views

Sort rectangles in a grid based on a comparison of the center point of each

If I have a grid of rectangles and I move one of the rectangles, say above and to the left of another rectangle, how would I resort the rectangles? Note the rectangles are in an array, so each ...
2
votes
1answer
102 views

Sorting with continous input

I'm designing (not writing, yet) a task scheduler system for a complex video game. The rest of the program passes it objects containing a function and some metadata including an estimation of how much ...
1
vote
3answers
614 views

Sort an array in a specific order - not ascending/descending

I'm working on an algorithm that works best if the inputs are passed to it in a particular order, so I want to sort them that way. The difference is drastic enough for me to consider re-sorting the ...
5
votes
1answer
831 views

Sorting versus hashing

My problem is as follows. I have an array of n strings with m < n of them distinct. I want to create a one-to-one function which assigns each of the m distinct strings to the numbers 0 ... m-1. ...
13
votes
2answers
516 views

Trying to understand the 2N lnN compares for quicksort

I was going through the analysis of quicksort in Sedgewick's Algorithms book. He creates the following recurrence relation for number of compares in quicksort while sorting an array of N distinct ...
1
vote
1answer
317 views

Advantage of 2-way merge sort against n-way

It's known 2-way Merge sort takes N*logN time. I wonder, what would be the running time if we split an array of the size N into N subarrays and then do the same thing as we would do for 2-way Merge? ...
9
votes
7answers
7k views

Why is binary search,which needs sorted data, considered better than linear search?

I have always heard that linear search is a naive approach and binary search is better than it in performance due to better asymptotic complexity. But I never understood why is it better than linear ...
6
votes
3answers
1k views

Why is Quicksort called “Quicksort”?

The point of this question is not to debate the merits of this over any other sorting algorithm - certainly there are many other questions that do this. This question is about the name. Why is ...
1
vote
2answers
1k views

Radix exchange sort implementation?

I need a little help understanding the implementation of radix exchange sort algorithm. Radix exchange (I don't know if it's the exact name in english based literature) is a lot similar to quicksort, ...
1
vote
3answers
439 views

Sorting and averaging the highest values of pixel data

Currently, I am using Android/Java. I am looking for the most efficient means to determine the average of the highest 100 pixel values taken from a greyscale preview. The preview part I am more or ...
7
votes
3answers
848 views

Why don't computers come with specialized hardware such as sorting networks?

Instead of programming the way we do, why don't we make specifications of common tasks such as "sorting", and then let the environment compile it to make best use of it's hardware? This way, we could ...
1
vote
3answers
208 views

Binary Search Programming implementation

Binary Search, as we all know requires the elements to be sorted. But we have to take care of unsorted elements too, in the worst case. If the input size is very large, is it a good idea to sort the ...
0
votes
1answer
2k views

Sorting an ArrayList by a Split Value [closed]

I am attempting to create an list which should be sorted by a particular field in a colon separated string. I have an array of strings with the following values: name1:535 name2:697 After sorting ...
1
vote
1answer
424 views

Custom Alphabetic Sorting of Array in Java

I have a requirement to read a text file with lines in tag=value format and then output the file with specific tags listed first and the rest sorted alphabetically. The incoming file is randomly ...
1
vote
1answer
6k views

Quicksort and middle pivot

I am having a head ache understanding quicksort with middle pivot. I found lot of explanations about using left most or right most, but not many about a middle one. Can I safely assume these?: If ...
2
votes
3answers
158 views

What kind of algorithm could be used to produce an ordering which maximizes # of satisfied 'less than' constraints?

Let's say I have a set of items {e1, e2, ..., en}, and I also have a set of constraints {c1, c2, ..., cm}, with ci := ej appears before ek, for some j and k. I want to produce an ordering of my items ...
33
votes
6answers
3k views

I'd like to write an “ultimate shuffle” algorithm to sort my mp3 collection

I'm looking for pseudocode suggestions for sorting my mp3 files in a way that avoids title and artist repetition. I listen to crooners - Frank Sinatra, Tony Bennett, Ella Fitzgerald etc. singing old ...
2
votes
4answers
2k views

Applications of heapsort

Heapsort is a sorting algorithm that has a time complexity of O(nlogn), and performs sorting using O(1) space complexity. However, I know that because it's unstable, it doesn't find many applications ...
0
votes
2answers
569 views

Does this version of insertion sort have O(n) complexity for best case?

for ( i = 1 ; i <= N ; i++ ) { for ( j = 0 ; j < i ; j++ ) { if ( arr[j] > arr[i] ) { temp = arr[j] ; arr[j] = arr[i] ; for ( k = i ; k > j ; k-- ) ...
0
votes
3answers
3k views

What are the most popular sorting algorithms in practice? [closed]

Although I suspect the answer to this question may be something along the lines of "popularity is irrelevant; each algorithm has its trade-offs", I'm interested in a list of popular sorting algorithms ...
1
vote
4answers
305 views

How important is understanding the coding behind sorts?

First off, if this is in the wrong place I apologise. I wasn't too sure on which of the Stack Exchange sites to ask it. I am studying Software Development at university, on a one year conversion ...
1
vote
3answers
606 views

Should I calculate hotness of a post on request or pre-calculate it?

Here is the Reddit's hot algorithm: cpdef double _hot(long ups, long downs, double date): """The hot formula. Should match the equivalent function in postgres.""" s = score(ups, downs) ...
5
votes
2answers
4k views

Help understanding MapReduce Sort example

From Section 5.3 of Google's paper describing MapReduce. "A Map function extracts a 10-byte sorting key from a text line and emits the key and the original text line as the intermediate ...
2
votes
1answer
2k views

Fastest Haskell library sort implementation

I am implementing an application in Haskell and, for sorting, I use the library function Data.List.sort. However, I was wondering whether this is the fastest sort implementation in the Haskell ...
5
votes
2answers
4k views

How to handle sorting of complex objects?

How would one sort a list of objects that have more than one sortable element? Suppose you have a simple object Car and car is a defined as such: class Car { public String make; public ...
2
votes
2answers
797 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 ...
0
votes
1answer
592 views

Efficient way to sort large set of numbers

I have to sort a set of 100000 integers as a part of a programming Q. The time limit is pretty restrictive, so I have to use the most time-efficient approach possible. My current code - ...
6
votes
5answers
457 views

Type of AI to tackle this problem?

I posted this on stackoverflow but want to get your recommendations as well as a user on overflow recommended I post it here. I'm going to say from the beginning that I am not a programmer, I have a ...
3
votes
3answers
604 views

Data structure: sort and search effectively

I need to have a data structure with say 4 keys . I can sort on any of these keys. What data structure can I opt for? Sorting time should be very little. I thought of a tree, but it will be only help ...
2
votes
1answer
512 views

Comparison of my own Insertion Sort versus the standard algorithm

I come from a background of making MVC websites and HTML5 applications, and have recently decided to dive into the sort of stuff i wasn't taught at university, namely the things most people would ...
-2
votes
3answers
176 views

Sorting months with pre-defined order?

I want to sort the months of the year starting at any month, but January needs to show up after December if January isn't the starting point. Can I do that in an array or do I need a special data ...
5
votes
2answers
995 views

What's the best way to manage list item sort order with Drag & Drop UI?

I have a list of Students that I should display to user on a web page in tabular format. The items are stored in DB along with SortOrder information. On the web page, user can rearrange the list ...
1
vote
1answer
1k views

sorting using a custom definition of “>” and “< ” in python

suppose I have a custom function such as def greater(a, b): if (a % b) % 2 == 0: return 1 return 0 It defines how to compare two numbers and determine which is greater. In this ...
2
votes
4answers
5k views

What sorting algorithm does STL use?

I recently started using <vector.h> library and I was wondering, since all the operations are already implemented, IF the method of the sorting algorithm is the most efficient one. Everything ...
1
vote
7answers
10k views

Merge sort versus quick sort performance

I have implemented merge sort and quick sort using C (GCC 4.4.3 on Ubuntu 10.04 running on a 4 GB RAM laptop with an Intel DUO CPU at 2GHz) and I wanted to compare the performance of the two ...
1
vote
1answer
259 views

Algorithm for determining grid based on variably sized “blocks”?

I'm trying to convert a set of "blocks" in to a grid-like layout. The blocks have a width of either 25%, 33%, 50%, 66%, or 75% of their container and each row of the grid should try to fit as many ...
8
votes
2answers
891 views

Why doesn't java use a radix sort on primitives?

java.util.Arrays.sort(/* int[], char[], short[], byte[], boolean[] */) is implemented as a 'tuned quicksort' rather than a radix sort. I did a speed comparison a while ago, and with something like ...
1
vote
1answer
346 views

Need help with algorithm for sorting list

The answer is probably obvious but not to me at this moment, so I was wondering if somebody who is better with sorting algorithms can help lead me in the right direction. This is not homework, I am ...
12
votes
7answers
16k views

Sort algorithms that work on large amount of data

I am looking for sorting algorithms that can work on a large amount of data, i.e. that can work even when the whole data set cannot be held in main memory at once. The only candidate that I have ...
7
votes
5answers
6k views

Why do some sorting methods sort by 1, 10, 2, 3…?

I've noticed than many numerical sorting methods seem to sort by 1, 10, 2, 3... rather than the expected 1, 2, 3, 10... I'm having trouble coming up with a scenario where I would need the first method ...
4
votes
3answers
2k views

Basic premise on counting sort. How is k related to to Big Oh?

I am reading (Cormen) on counting sort. I understand the structure of the algorithm but the statement: In practice, we usually use counting sort when we have k = O(n), in which case the ...
10
votes
5answers
1k views

Algorithm refresher. Why is heapsort an insort algorithm?

I can not see why the heapsort is considered an inplace sorting algorithm. I mean an extra data structure populated with the elements of the array to be sorted i.e. a heap, is used to assist in the ...
17
votes
3answers
1k views

Java and .NET: Why different sorting algorithms are used by default?

Just wondering why Java and .NET Framework uses different sorting algorithm by default. In Java Array.Sort() uses Merge Sort algorithm by default and as Wikipedia.com says: In Java, the ...
5
votes
3answers
2k views

does quicksort provide less swapping step?

So far, most of the fastest and common sorting method is quicksort. Although it has its pro and cons. However, i'm thinking that although this sorting method is fast but does it provide shortest ...
8
votes
3answers
339 views

Data “unsort” / homogeneity algorithm

In an attempt to not reinvent a wheel, I'm asking if anyone has ideas on a data homogeneity algorithm. A brief example: My data has several elements maybe like Number Color Fruit Letter There ...