# Tagged Questions

For questions about sorting algorithms and their speed and complexity.

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### Quickest sorting algorithm for sorting a low number of integers

I am making a program on my spare time that I want to run as quickly as possible. The program is written in C. A large set of the procedures operate on pointers to 7 integers that are sorted by their ...
98 views

### multiple comparison sorting

I have a set of songs where I want to sort them by a particular quality. In order to do this (by crowdsourcing) I will present users with a comparison between two songs. The user will then choose ...
332 views

### In-place merging of sorted intervals in an array?

So I have code producing k sorted intervals in an n-sized array. What I'm brainstorming is the possibility of in-place merge of these intervals into a single sorted interval/array. The problem is ...
71 views

### Sorting list and changing same values to nearly the same

I have a list of doubles that need to be sorted and changed so that there are no two numbers that are the same (difference smaller then 0.05) and I need to do it fast. I don't care about preserving ...
467 views

### Is there any language-agnostic specification for “String Natural Sorting Order”

As I painfully try to find a good natural sorting algorithm written in JavaScript I then stumble upon a bunch of different implementations, & interesting blog posts & answers on Stack Overflow....
139 views

### An algorithm to implement SQL's ORDER BY with TOP/LIMIT or OFFSET/FETCH

Is there a general algorithm to implement SQL's ORDER BY with OFFSET/LIMIT more efficiently than sorting all the records? The algorithm for a simple TOP x is easy enough. It takes one full pass ...
8k views

### What makes for a bad case for quick sort?

I am learning about quicksort and want to illustrate different arrays that quicksort would have a hard time on. The quicksort I have in mind does not have an initial random shuffling, does 2 partition,...
210 views

### How to efficiently sort a recursively defined Stack?

I am trying to implement a recursively defined Stack and sort it in Java. I don't have a particular usage of this program in mind. I found this approach of stack implementation a bit useful while ...
681 views

### Count Sort Algorithm efficiency

As I read a book about "Algorithm Analysis", I came across count_sort Algorithm. However, I have read elsewhere that "Quick Sort/ Merge Sort" are the best and the most efficient sorting algorithms. I ...
779 views

### Dual pivot quicksort in face of expensive swaps

I was told this is better place to ask this TLDR Has anyone tested dual pivot quicksort performance with expensive-to-swap elements? It seems that in this case, it should massively underperform ...
596 views

### Level order sorted binary tree from a binary tree

Lets suppose we have a binary tree . Tree node structure is as struct node { int val ; struct node *left , *right ; } Now we have to sort the tree in level order manner . For example lets ...
19k views

### What does it mean for a sorting algorithm to be “stable”?

In reading about various sorting algorithms I've seen it mentioned that some are "stable" and some are not. What does that mean, and what tradeoffs are involved on that basis when selecting an ...
639 views

### How can I rank teams based off of head to head wins/losses

I'm trying to write an algorithm (specifically in Ruby) that will rank teams based on their record against each other. If a team A and team B have won the same amount of games against each other, then ...
877 views

### Tournament bracket method to put distance between teammates

I am using a proper binary tree to simulate a tournament bracket. It's preferred any competitors in the bracket that are teammates don't meet each other until the later rounds. What is an efficient ...
6k views

### Why is time complexity of k-way merge sort O(nk^2)?

I'm comparatively new to algorithm analysis and am taking a related course on coursera where I came accross k way merge sort. The time complexity of 2 way merge sort is n log2 n, of 3 way merge sort ...
3k views

### comparison of floating point numbers vs. comparsion of Integers in C [closed]

Does comparison of floating point numbers takes (considerably) longer time than comparison of Integers in C? I just wrote a C program of heap sort to sort floating point numbers. I am on ubuntu 14....
162 views

### Maintaining sorted Array speed

I have a for loop running over a list of objects like: [{a: 2001, b: "hello"}, {a: 54, b: "hi"}....] In this loop, I filter out objects based on certain field values (like, b == hello?) and create ...
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### Algorithm for inserting into sorted subset

A is a sorted list. B is a sorted list, and a subset of A. If an element is inserted into A at index i what's the most efficient way to determine the correct index i' for it's position in B? Given ...
107 views

### Set distances algorithm question

I have multiple sets containing integers. An integer maybe present in one set or multiple sets. I would like to find/match the sets with the most common integers. Example s1 {1, 2, 3, 4} s2 {1, 3, 4, ...
896 views

### Python sorted iterable set, modifiable during iteration

I am looking for a datastructure to handle cycling through a large number of ordered subroutines, some of which are active, most of which are not. I am thinking I need an implementation of a python ...
281 views

### Sorting an array when values are decreased by each swap [closed]

Recently in an interview I come across a question: We have an unsorted array, we need to sort it with minimum number of swap. We have in sort a 'tax' of 1 is deducted from the number we are ...
201 views

### Short Sequential Search vs. Regular Sequential Search

Assuming a list of elements is sorted in ascending order, we search sequentially from the first element comparing the target to successive elements either until we find the target (succeed) or until ...
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### expressing the speed of a sorting algorithm

How would I express the speed of the following sort algorithm? I know bubblesort is n^n (er, I mean n^2...as someone pointed out below). In the following the array decreases each time you call it ...
405 views

### Fully Stable, In-Place Unique Algorithm in O(n)

Is there an algorithm that, given a sorted array, swaps all the first unique elements to the beginning of the array and the duplicates to the end, while remaining stable for both the unique subarray ...
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### Algorithm that determines relevant attributes in ordered list

Suppose I have a list of objects sorted by a person based on that person's subjective taste. Let's assume that this person is being somewhat consistent in their sorting and that there are quantifiable ...
16k views

### Quickest way to split a delimited String in Java

I am building a Comparator that provides multi-column sort capability on a delimited String. I am currently using the split method from String class as my preferred choice for splitting the raw String ...
973 views

### which sorting algorithms is using OrderBy

I am litle curious about what sorting algorithm is using OrderBy (linq to objects). quicksort? heapsort? introspective sort ? As i see in MSDN documentation List.Sort is using introspective sort: ...
471 views

### Is there any sorting algorithm which is not inherently sequential and is task distributable?

After googling for a couple hours, I came to a conclusion that all sorting algorithms are inherently sequential which can be data distributed but not task distributable. Is there any algorithm which ...
3k views

### Sorting an array of numbers with decimal places

Suppose I have an array of float values in the following format: { 1.34, 1.15, 1.1, 1.2, 1.26, 1.10, 1.20, 1.17 } Suppose they have been provided by user input (or some other mechanism), where the ...
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### How to queue work orders by date and priority?

In my organization I work on orders based on date, so earliest work orders first. We also have an option for order to be marked "priority" in which case those orders are done first but not always. I'...
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### Looking for monotonically increasing (integer) hash function

I'm looking for a HashFunction(X,Y: Integer): Integer that is monotonically increasing on X, then Y. So: HashFunction(x1,y1) > HashFunction(x2,y2) if x1>x2 HashFunction(x,y1) > HashFunction(x,y2) if ...
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### 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 ...
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). ...
3k 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 ...
188 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,...
1k 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 ...
617 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 ...
111 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 ...
741 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 ...
2k 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. ...
616 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 ...
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### 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?
14k 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 ...
2k 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 ...
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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, ...
628 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 ...
1k 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 ...
283 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 ...