# Questions tagged [comparison]

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### Ideal less-than-or-equal circuit for multiple inputs?

I'm interested in what the best way is to design a circuit that takes multiple values as input, and then outputs which value is the lowest. If multiple values are the lowest, it outputs "true&...
137 views

### Comparison-based computation: percentage of current software development?

Vol. III of The Art of Computer Programming, chapter 5 (Sorting, intro) mentions: Computer manufacturers of the 1960s estimated that more than 25 percent of the running time on their computers was ...
1 vote
120 views

### How do you write a logic function to determine if one 2s complement binary number is less than another?

Working on logic design in class, and I'm trying to figure out how to write a specific logic function [and by write, I mean something along the lines of (x NOR y) OR (a NOR b), for example] It asks to ...
30 views

### Where can I find a list of logics with their corresponding calculus and computation phenomena?

I was watching some lectures by Prof. Pfenning on Proof Theory. Between 5:30 and 15:00, he gave a list for some different kinds of judgments along with their calculus and computation phenomena that ...
38 views

### Compare list of parameters with each other and sort them from most to least selected

I want to sort the list of parameters (p1, p2, p3, p4, ..., pn) according to their importance. All parameters have to be compared with each other at best once, but not less than once. The person will ...
291 views

### Can we create a decision tree for any comparison sorting algorithm even if it is very complicated?

I am reading an algorithm book. Any comparison sort must make $\Omega(n\log(n))$ comparisons in the worst case to sort $n$ elements. Can we create a decision tree for any comparison sorting algorithm ...
1 vote
120 views

### Is there an efficient algorithm for finding a minimal common subset of pairwise distinct bits in a set of bit strings?

I am working on an efficient mapping function represented as a directed graph. In essence, it is a sort of radix trie. A path must be formed from a bit string [string hereon] efficiently. To do this, ...
1 vote
55 views

### Efficient comparison, using only sum, product, difference, and conditional jump if zero

I was wondering how small we could make the instruction set of a typical machine that supports a single datatype: arbitrary integers. If you need a heap, you declare an integer variable $h$ where you ...
61 views

### Can you compare large numbers this way?

If you created two very large numbers represented by binary data (perhaps using sha512 with random input for each hash) could you determine what binary block is numerically larger by iterating over ...
1 vote
61 views

### Examples of comparison-based algorithms that are not a sort or a search over lists

Can you share examples of comparison-based algorithms used in practice that are not a sort or a search over lists? Heapify is an example of a comparison-based algorithm that is neither a sort nor a ...
1 vote
593 views

### Best-case time: comparison-based sorting on a list of size n must make n-1 comparisons (reference to proof)

I am looking for a reference to a proof that for every list of size $n$ comparison-based sorting cannot make less than $n-1$ comparisons. Do you have a reference of a book that covers it (with page ...
28 views

### Comparing various ways to move a game actor having time-dependent velocity

Assume I have a game actor (name it MyActor for further references) to be moved up and down according to $z=f(t)=A\sin \omega t$ (or any non constant velocity). The ...
141 views

### Algorithm best compare similarities between two data sets in percentage

I'm trying to create an algorithm that finds the percentage of similarity between two subjects with sets of survey questions. Example: Q1: Do you prefer physically demanding tasks? A1: Nope Maybe Yes -...
106 views

### Average number of comparison for 3 items

What is the average number of comparisons performed when sorting 3 items? The question is based on the above picture.
1 vote
39 views

### n-bit ALU usually do comparison operation on maximum n/2-bit or n-bit?

For n-bit ALU is equal-to operation and similar comparisons generally limited to n/2-bit words, or n-bit?
1 vote
534 views

### Sorting an array with x sorted subarrays

I have been given two True/False questions regarding sorting an array. The questions are as following - Question A Given an array A with 3n keys that contains three equal parts A[1,n], A[n+1,2n] and ...
209 views

### What is a sorting algorithm that is robust to a faulty comparison?

I want to sort a list of n items with a comparison sort. However, one of the comparisons made by the algorithm will be flipped from what it's supposed to be. ...
1 vote
792 views

### What is the best way to compare two images for similarity if the brightness of the second image was changed?

I calculate similarity percent between two images. Another image is the same with changed brightness. I've already tried comparing by pixel (euclidean distance for grayscale and 0/1 values), comparing ...
1 vote
118 views

### QuickSort when the range of data is known

In QuickSort Algorithm, the pivot is chosen as the first element or a randomised element. However, if the range of data to be sorted is known, For example, from 1 to 100, and they are mostly equally ...
1k views

### Algorithm to compare two data sets

I have two data sets of a particular structure: ...
104 views

### Constraint satisfaction problem: solve system, then evaluate whether many additional constraints are satisfied one at a time

I have a system that consists of binary inequality constraints between variables, plus some indicator variables that can assume only two values: ...
1 vote
88 views

### Finding maximum of $n$ many $m$-bit integers

Suppose you want to determine the largest number in an $n$-element set $X = (x_1, x_2, \dots , x_{n})$, where each element $x_i$ is an integer between $1$ and $2^m − 1$. Describe an algorithm that ...
42 views

### Longest palindrome substring in logarithmic runtime complexity

In a palindrome of size N, the amount of candidates for the longest palindrome is N^2. Therefore, the information theoretic lower bound (IBT) should be lg(N^2), which is equivalent to a runtime ...
5k views

### Why do we use the number of compares to measure the time complexity when compare is quite cheap?

I think one reason a compare is regarded as quite costly is due to the historical research as remarked by Knuth, that it came from tennis match trying to find the second or third best tennis player ...
346 views

### Sorting array of strings (with repetitions) according to a given ordering

We get two arrays: ordering = ["one", "two", "three"] and ...
549 views

### Recurrence Relation of Ternary search and the number of comparisons with binary search

i was reading the binary search and ternary search algorithms. But i had a doubt with recurrence relation of ternary search as somewhere it is T(n/3)+c and T(2*n/3)+c. I want to know which one is ...
1k views

### Minimum number of comparision to find the third largest element in an array of distinct integers?

For the second largest element, I know that the formula is $n+ \lceil\log n \rceil -2$ Is there any formula for the third largest element? and if so, what is the derivation? 34 views

### Algorithm for comparing object dates and types

I'm looking for a good / efficient algorithm to compare classes of driver licences (or any type of similar objects) and their dates, so that they do not overlap and come in certain order. eg. We have ...
171 views

### Goemans' Extended Formulation of the Permutahedron And Comparator Networks that are not Sorting Networks

I am interested in using Michel Goemans' extended formulation first developed for the permutahedron to study comparator networks that are not sorting networks. In his paper "Smallest Compact ...
1 vote
32 views

### How to justify using available code (in different language) for comparing algorithms [closed]

I have proposed an algorithm for a scheduling problem in a submitting paper. In the revision, the reviewer asked us to compare with another algorithm in the literature. Our algorithm is in MATLAB, and ...
1 vote
1k views

### Turing machine - compare two words

I have a simple turing machine with single tape. I need to compare two words <w1>$<w2>$ and write output. Language is all letters and numbers. I did ...
205 views

### Why is finding minimum number of comparisons to sort $n$ elements so difficult?

In The Art of Computer Programming 2nd Ed, Vol 3, Section 5.3.1 then discuss a function $S(n)$ which is define as: $S(n)$ : The minimum number of comparisons that suffice to sort $n$ elements. ...
46 views

### Finding maximum takes at least $\lceil n/2 \rceil$ comparisons

We are given an array $A$ with $n$ elements, $n \in \mathbb{N}$ and all elements are in the set $\{1,2,3, \cdots, n \}$. I want to prove that finding the maximum in $A$ (that is, outputting the index ...
236 views

### Are comparison sort algos appropriate for SUBJECTIVE sorting?

I've been tasked with creating an online feature that ranks 50 fantasy characters from a variety of domains based on combat acumen and polls users one which one is the most powerful based on their ...
1 vote
109 views

### An algorithm to drop low-priority items from a heap-based priority queue

I am looking for an efficient algorithm to drop from a complete binary min heap all items whose weight exceeds a given value. (Or, equivalently, to drop from a priority queue realised by such a heap ...
1 vote
892 views

### Sorting lower bounds for almost sorted array

Can't find a good way to tackle the problem. Would appreciate any help. $A$ is an $n$ items array from an ordered set, in which every item is at most $\log n$ indices away from its position in the ...
461 views

### d-ary heap implementation vs Fibonacci heap implementation Dijkstra performance comparions

Let's say that Dijkstra’s algorithm with the priority queue using a d-ary heap. if adjusting d, we can try to achieve the best runtimes for the algorithm with d being $\sim |E|/|V|$. Then for a ...
102 views

### Optimize sorting matrix entries by row and column

I am writing a routine to store an $M$-by-$N$ sparse matrix in a balanced binary tree. The insertion routine calls a comparison function to determine where a new matrix entry $(i,j)$ should be ...
4k views

### How to compare an element with other elements within an array efficiently for a condition

I need to compare each index with one another and associated array value as well. For example, ...
182 views

### sort n numbers in the range [0,1] without multiplying or dividing

Given an array with n real numbers, each in the range [0,1], I need to sort them. Moreover, the only operations that are allowed are comparisons or copying. It means I cannot multiply or divide the ...
1 vote
54 views

### Merge unstructured with structured data

We have a database with well-formated and structured data. From time to time we get Excel - files from our clients. This Excel Files have to be imported to the database. It it very important that we ...
13k views

### Data structure or algorithm for quickly finding differences between strings

I have an array of 100,000 strings, all of length $k$. I want to compare each string to every other string to see if any two strings differ by 1 character. Right now, as I add each string to the ...
1 vote
128 views

### What is the name for the comparison used in C's memcmp?

The C memcmp function (and strcmp) does a comparison similar to the function below for comparing integers: ...
106 views

### Compare two atan2

I tried to implement points location algorithm using Fortune's algorithm to get Voronoi diagram and another sweepline algorithm to locate many points in $O(n\cdot\log(n))$. If there are multiple ...
916 views

### Turing Machine for $\{w\# w ' |$ where $w < w'$ lexicographically, and $w,w'\in \{0,1\}^* \}$

I am blocked with this question for a long time. $L = \{w\# w ' |$ where $w < w'$ lexicographically, and $w,w'\in \{0,1\}^* \}$ I am trying to find A Deterministic Turing Machine for L. A Non-...
1 vote
1k views

### finding best n players in minimum number of comparisons

I am trying to find out if there is any generic way to find out first to nth best player in a tournament if n is less than the square root of input size i.e. 5 best players in the sample size of 25 ...
I'm currently doing an exercise that asks to prove that Standard-Heapsort requires at fewest $\frac{1}{8} n \log(n) - O(n)$ comparisons, in its best case. In its average case, Heapsort only requires $... 2 votes 2 answers 2k views ### Proving at least$n-1$comparisons are needed to test if an array is sorted so I need to prove the following: Prove that$n-1$comparisons are sometimes necessary to test whether an array with$n$distinct elements is sorted in increasing order, for any$n \geq 1$. The ... 1 vote 1 answer 389 views ### Identify similar functions I was wondering if there is any technique in order to recognize similar functions behaviour. In particular, suppose that I implement two functions$f$and$g$in a certain programming language$P\$ and ... 