# John D'Errico

### Retired

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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**Content Feed**

Solved

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 ...

bijna 3 jaar 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). ...

bijna 6 jaar 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). ...

bijna 6 jaar 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: ...

ongeveer 6 jaar 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 ...

ongeveer 6 jaar 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...

ongeveer 6 jaar 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...

ongeveer 6 jaar ago

Solved

Perimeter

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

ongeveer 6 jaar 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. ...

ongeveer 6 jaar 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...

ongeveer 6 jaar 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...

ongeveer 6 jaar 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...

ongeveer 6 jaar 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...

ongeveer 6 jaar 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 ; ...

meer dan 7 jaar 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,...

meer dan 7 jaar ago | 2 | 27 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...

meer dan 7 jaar 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...

meer dan 7 jaar 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...

meer dan 7 jaar ago | 1 | 23 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 ...

meer dan 7 jaar 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.

meer dan 7 jaar 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.

meer dan 7 jaar 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 = ...

meer dan 7 jaar 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...

meer dan 7 jaar ago | 4 | 36 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...

meer dan 7 jaar 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...

meer dan 7 jaar 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...

meer dan 7 jaar 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...

meer dan 7 jaar 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...

meer dan 7 jaar ago | 9 | 229 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 ...

meer dan 7 jaar ago

Solved

Determine Whether an array is empty

Input a matrix x, output y is TRUE if x is empty, otherwise FALSE.

meer dan 7 jaar ago