John D'Errico

Last seen: 1 day ago | Active since 2006

Followers: 41 Following: 0

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A retired applied mathematician, consultant, sometime mechanical engineer, numerical analyst, woodworker, bridge player. Please DON'T contact me, as too many students then decide I am their personal consultant if I allow it. I won't do consulting by mail.

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Divisible by 2
This is the first problem in a set of "divisible by x" problems. You will be provided a number as a string and the function you ...

5 years ago

Solved

Edges of a n-dimensional Hypercube
Return the number of edges on an <http://en.wikipedia.org/wiki/Hypercube _n_-dimensional hypercube> (with an integer n ≥ 0). ...

8 years ago

Solved

Dots in a Circle
Return how many integer grid points there are inside a circle of radius _r_ centred at (0,0) (including points on the edge). ...

8 years ago

Solved

The average of the second largest values
Given a matrix, find the average of the second largest values in each row. The same value does not exist on a row. Example: ...

8 years ago

Solved

Fibonacci-Sum of Squares
Given the Fibonacci sequence defined by the following recursive relation, * F_n = F_(n-1) + F_(n-2) * where F_0 = 0 and F_1 ...

8 years ago

Solved

Volume of a Simplex
Return the volume of a <http://en.wikipedia.org/wiki/Simplex regular _n_-simplex> with a unit side length. Results are up to...

8 years ago

Solved

Volume difference between Ellipsoid and Sphere
Given an ellipsoid of semi principal axis (a,b,c) find the volume of the difference between this ellipsoid and the sphere with...

8 years ago

Solved

Perimeter
Given a sequence of points forming a closed path (first and last points are coincident) return the perimeter value. For example...

8 years ago

Solved

Return the Fibonacci Sequence
Write a code which returns the Fibonacci Sequence such that the largest value in the sequence is less than the input integer N. ...

8 years ago

Solved

Find nearest prime number less than input number
Find nearest prime number less than input number. For example: if the input number is 125, then the nearest prime number whi...

8 years ago

Solved

sum of non-primes
The sum of the non-primes no larger than 10 is 1+4+6+8+9+10=38 Find the sum of all the positive non-prime integers that do no...

8 years ago

Solved

Extra safe primes
Did you know that the number 5 is the first safe prime? A safe prime is a prime number that can be expressed as 2p+1, where p is...

8 years ago

Solved

Pernicious Anniversary Problem
Since Cody is 5 years old, it's pernicious. A <http://rosettacode.org/wiki/Pernicious_numbers Pernicious number> is an integer w...

8 years ago

Solved

Get linearly independent vectors of given matrix.
Get a set of linearly independent vectors from the rows of a given matrix. Example matrix=[ 3 -1 0 0 ; ...

9 years ago

Problem

Euclidean distance from a point to a polynomial
A not uncommon problem in the area of computational geometry is to find the closest point to a straight line from a given point,...

9 years ago | 3 | 37 solvers

Solved

For given xx,x, y vectors build spline of x and y and find yy values for xx vector.
For given xx,x, y vectors build spline of x and y and find yy values for xx vector. Example x = [ 1.0000 1.5000 2.00...

9 years ago

Solved

What's size of TV?
Many people buy TV. Usually they ask about diagonal. But also important are width and height. Let's assume that all TV have rati...

10 years ago

Problem

Euclidean inter-point distance matrix
The Euclidean distance between two points in a p-dimensional space is a really common thing to compute in the field of computati...

10 years ago | 1 | 29 solvers

Solved

Prime number removal
remove all prime numbers from the input e.g. input = 1 2 3 4 5 6 7 8 9 10 11 12 ...

10 years ago

Solved

Determine the roots of a cubic equation
Given the coefficients a, b, c, and d of a cubic equation, a*x^3 + b*x^2 + c*x + d = 0, determine its roots.

10 years ago

Solved

Roots of a quadratic equation.
Calculate the roots of a quadratic equation, given coefficients a, b, and c, for the equation a*x^2 + b*x + c = 0.

10 years ago

Solved

Sum of digits of powers of 2
Given n, first, calculate the number 2^n. Then, sum the digits that comprise that number. For example: Input: n = 7 2^n = ...

10 years ago

Problem

Simpsons's rule (but not Homer Simpson)
I wonder what Homer Simpson would have thought of Simpson's rule? Somehow I doubt his thoughts would have included the phrase Ne...

10 years ago | 4 | 50 solvers

Solved

Right and wrong
Given a vector of lengths [a b c], determines whether a triangle with those sides lengths is a right triangle: <http://en.wikipe...

10 years ago

Solved

Make a Palindrome Number
Some numbers like 323 are palindromes. Other numbers like 124 are not. But look what happens when we add that number to a revers...

10 years ago

Solved

Solve the Sudoku Row
*Description* A simple yet tedious task occurs near the end of most Sudoku-solving algorithms, computerized or manual. The ta...

10 years ago

Solved

Sums of cubes and squares of sums
Given the positive integers 1:n, can you: 1. Compute twice the sum of the cubes of those numbers. 2. Subtract the square...

10 years ago

Problem

Sums of cubes and squares of sums
Given the positive integers 1:n, can you: 1. Compute twice the sum of the cubes of those numbers. 2. Subtract the square...

10 years ago | 9 | 378 solvers

Solved

Project Euler: Problem 6, Natural numbers, squares and sums.
The sum of the squares of the first ten natural numbers is, 1^2 + 2^2 + ... + 10^2 = 385 The square of the sum of the first ...

10 years ago

Solved

Determine Whether an array is empty
Input a matrix x, output y is TRUE if x is empty, otherwise FALSE.

10 years ago