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Questions tagged [matrix]

In mathematics, a matrix (plural matrices) is a rectangular array of numbers, symbols, or expressions, arranged in rows and columns. The individual items in a matrix are called its elements or entries.

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Reversing a Matrix

I took the idea from Reversing a matrix in C# and decided to write my own matrix-reversing code. Is there anything that I can do to make it even better? ...
43k views

Given N*N matrix, rotate it by 90 degree to left and right without extra memory

I'm looking for a code review, clever optimizations, and good coding practices. Unit testing has been a visual inspection and concluded expectations match. Also, is the space complexity of the extra ...
249 views

Matrix reloaded … or reversed

I have written this Matrix class after posting an answer to Malachi's rags-to-riches question. The initial purpose had been to reverse a matrix represented by a 2D ...
627 views

Leetcode 54: Spiral Matrix

Problem statement Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order. For example, Given the following matrix: [   [ 1, 2, 3 ], ...
5k views

2048 merge function

From: Principles of Computing Part 1 Course on Coursera I got -2 pts on my OWLTEST which uses Pylint for style guide. The error states: Too many branches (17/12) function "merge", line 7 ...
4k views

Matrix rotation algorithm

This is the Matrix Rotation problem from hackerrank.com. You are given a 2D matrix, $a$, of dimension $M×N$ and a positive integer $R$. You have to rotate the matrix R times and print the ...
2k views

Converting Data in Rows and Columns to Rows in VBA for Excel

I have a working VBA script for Excel that converts a matrix of data with multiple records in per row to multiple rows with one record per row. A StackOverflow user told me that the code could use ...
182 views

Magic Square (Python)

Problem Write a method to return a boolean if an input grid is magic square. A magic square is a $NxN$ square grid (where N is the number of cells on each side) filled with distinct positive ...
428 views

HackerRank NCR codesprint: Spiral Message

Problem statement: https://www.hackerrank.com/contests/ncr-codesprint/challenges/spiral-message You've intercepted an encoded spy message! The message originated as a single line of one or more ...
736 views

HackerRank - Queens Attack II - Java

The problem definition can already be found here. Given a chess board with dimensions n × n (where n is up to 100000) and the (r, c) positions of various obstacles, how many squares can a queen at a ...
3k views

A grid and a menu walked into a program

A program that creates a grid 10x10 and assigns a random number in each tile. It then asks you if you want to: create a new grid view the current one count how many of each number there are in the ...
3k views

Hackerrank Queen's Attack II

Problem statement A queen is standing on an $n$x$n$ chessboard. The chessboard's rows are numbered from $1$ to $n$, going from bottom to top; its columns are numbered from $1$ to $n$, ...
943 views

Find biggest basin

Problem Statement A group of farmers has some elevation data, and we’re going to help them understand how rainfall flows over their farmland. We’ll represent the land as a two-dimensional ...
785 views

Matrix rotation algorithm - follow-up

In a response to this post I wrote a solution in Python. It passed all the test cases given, so I would like help making it more pythonic and reducing the almost repeated lines. Link to the source of ...
2k views

Please check the code to see if there anything I can improve . Everyting is working as expected. matrix.h ...
979 views

SciPy sparse: optimize computation on non-zero elements of a sparse matrix (for tf-idf)

I have a sparse matrix (term-document) containing integers (word counts/tf) and I am trying to compute the tf-idf, for every non-zero value in the sparse-matrix. The formula for tf-idf I am using is: ...
143 views

Print matrix in spiral order in Scala

Problem: Given a square or rectangular matrix, print its element in spiral order. For example, if input matrix is this: ...
8k views

Calculate fibonacci in O(log n)

This program calculates the $n$th fibonacci number, in $O(\log n)$ time. I'm looking for code review, optimizations, and best practices. ...
451 views

Linear algebra, reduced row echelon form - function 1

This is a derivative post from here. This is just a general review, so the question is the same: Is there something... That you would consider as a bad practice and why? That is just bad in some ...
421 views

First template class - Matrix functions

This post has been answered and updated. This was the first time I've ever written a template class. I've spent probably a bunch of times re-writing matrix code for different types, different ...
2k views

Linear algebra, reduced row echelon form

The code that I am sharing here for you to review today, is a segment of a JavaScript library that I am going to write as time goes by for fun. It is only the two functions in the following code: <...
81 views

3-function program computing connected components of a point cloud given a distance matrix

I wrote this code in Haskell (instead of Python) for the educational benefit. Can anyone suggest ways to improve this code? I'm guessing that I'm using fromIntegral...
463 views

Portable multithreaded matrix multiplication in C

I essentially took this progam, and made it compile and run on Windows too. Also, I incorporated some nice points made by Toby Speight. matrix.h ...
7k views

Matrix multiplication using functions in C

This exercise surprised me a little bit. I did not expect that gcc (GCC 6.3.0 in the MinGW suite) would use the C11 standard by default, which I realised after I ...
913 views

Multithreaded matrix multiplication on Unix in C

I have this program for comparing serial and parallel matrix multiplication algorithms: matrix.h ...
246 views

Parse 2D matrix, 2 versions

I'm writing a little C program that computes matrices (for learning purpose). The matrix is fed through arguments in the following form : "{{43,543.324,34},{43,432,87}}" The user doesn't give the ...
11k views

Simple matrix class

I have built a 3D matrix class in C++, mainly for data I/O, for a project I am working on. The code works ok, but I would like you to help me improve it. Are there any bad programming practices I am ...
6k views

Neighbors of a matrix element

I would like a code review to make this code better, clear, and concise. The problem it's solving is as follows: Given a matrix, print the circumference of each of the items. For example: ...
185 views

Computing even huger Fibonacci numbers in Java

See the next iteration. I have that method for computing Fibonacci numbers $F_n$ ($n = 0, 1, 2, \dots)$, that relies on computing  A = \begin{pmatrix} 1 & 1 \\ 1 & 0 \end{pmatrix}^n. \$...
2k views

Reversing a matrix in C#

Implementation: ...
126 views

GeeksforGeeks: Rotate matrix by 90 degrees

Please review the code readability, I would like to have an easier to follow code. Thanks ...
815 views

A matrix with square diagonals and transpose being increments of other

Construct a matrix with the following property: North-west to South East diagonals are squares. Matrix[i][j] + 1 = Matrix[j][i] for each i less than j. Example of such m a matrix is here....
110 views

Template matrix class, second version

This is my first matrix class which I updated after already asking here already. The updated code is below. Are there any suggestions regarding member function parameters? Is there a convenient ...
851 views

Rotating a matrix in Java

Introduction This program is about rotating a matrix. For example, let the matrix be abcde fghij klmno pqrst Now, after rotating two steps clockwise we will ...
858 views

Effective Python 2/3 two-dimensional array initialisation

Recently I noticed that the idiomatic python two-dimensional array initialisation is extremely slow. I am wondering, is there a good, proper way of doing this simple task fast? Also, are those two ...
91 views

Code for number of routes possible of the given length between 2 given nodes

Recently I came across this problem , here is an excerpt of it, It is well known that the routing algorithm used on the Internet is highly non-optimal. A "hop", in Internet jargon, is a pair of ...
78 views

R Function to Generate Predictions from Ratings and Save Results

I am trying to generate predictions using the function below in combination with sapply. My actual datasets are very large, I am attempting to make 1.5 million predictions with this function and it is ...