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# Ryo Ishido

Last seen: 15 days ago Active since 2018

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Easy Sequences 11: Factorial Digits without Trailing Zeros
Here is an easy one... It is not difficult to count the number of digits of the factorial of a given number. For example for 'n...

29 days ago

Solved

Easy Sequences 10: Sum of Cumsums of Fibonacci Sequence
The function F(n) is defined as the set of Fibonacci numbers from the first up to the n-th. S(n) is the result of applying to F,...

1 month ago

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Easy Sequences 9: Faithful Pairs
A "faithful number" is a non-prime number that is one less or one more than some prime number but not both. For example, for num...

1 month ago

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Easy Sequences 5: Project Euler Problem 1 - Again!
We are all familiar with Project Euler Problem 1. This time let's try it on bigger multiples and larger range. Find the sum of ...

1 month ago

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Easy Sequences 6: Coefficient sums of derivatives
Consider the polynomial function and its first-order derivative . The sums of the coefficients of P and P', are and , respecti...

1 month ago

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Easy Sequences 4: Eliminate the Days of Confusion
If a date is written in purely numeric format some dates can be confusing, if we don't know the date format used. For example, "...

2 months ago

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Easy Sequences 3: Prime 44-number Squares
The positive integers 62 and 238 are related. Their squares (3844 and 56,644) both end in '44'. In fact, 62 and 238 are the 3rd ...

2 months ago

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Easy Sequences 2: Trigonometric function with integral input and output
The function 'F', defined as: , will always return an integer if the input is a natural number (in radian...

2 months ago

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Easy Sequences 1: Find the index of an element
The nth element of a series A is defined by: . Obviously, the first element A(1) = 1. Given the nth element 'A(n)', find the val...

2 months ago

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Toeplitize a matrix
Similar to <http://www.mathworks.com/matlabcentral/cody/problems/3094-hankelize-a-matrix Problem 3094. Hankelize a matrix>, now ...

2 months ago

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Write a function man that takes a row vector v and returns a matrix H as follows..
Write a function called man that takes a row vector v as an input and returns a matrix H whose first column consist of the eleme...

2 months ago

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Hankelize a matrix
Similar to <http://www.mathworks.com/matlabcentral/cody/problems/42501-toeplitize-a-matrix Problem 42501. Toeplitize a matrix>, ...

2 months ago

Solved

Matrix of Multiplication Facts
This is James's daughter again, sneaking into his Cody account. Thanks to your help in my math class last year, I did great! B...

2 months ago

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Go to the head of the class!
You're given a matrix and a single number. If that number is in the matrix, reorder the matrix so that number is in the first r...

2 months ago

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Must be in the front row...
You are given a matrix followed by a single number. Your object is to write a script that will shift the matrix around so that ...

2 months ago

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Magnet and Iron
(Inspired from <http://www.mathworks.com/matlabcentral/cody/problems/112 Problem 112: Remove the air bubbles>) Iron (atomic n...

2 months ago

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Replace Nonzero Numbers with 1
Given the matrix x, return the matrix y with non zero elements replaced with 1. Example: Input x = [ 1 2 0 0 0 ...

2 months ago

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Matrix multiplication across rows
Given matrix m, return matrix n such that, rows of n are result of multiplication of the rows of the input matrix Example ...

2 months ago

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A matrix of extroverts
Now that the introverts have had their script, the extroverts spoke up (naturally!) and demanded one as well. You will be given...

2 months ago

Solved

Convert matrix to 3D array of triangular matrices
Given a 2D numeric array x in which each column represents the vectorized form of an upper triangular matrix, return a 3D array ...

2 months ago

Solved

Too Many Zeros, Dump Them!
Sometimes when I create a matrix, I use this syntax: a = zeros(1000,1000); But when the function ends, I find that I don'...

2 months ago

Solved

Enlarge array
Given an m-by-n numeric array (A) and a 1-by-2 vector (sz) indicating the dimensions [p q] to enlarge each element, return an (m...

2 months ago

Solved

Remove entire row and column in the matrix containing the input values
Remove the entire row and column from the matrix containing specific values. The specified value can be a scalar or a vector. Fo...

2 months ago

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frame of the matrix
Given the matrix M, return M without the external frame.

2 months ago

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subtract central cross
Given an n-by-n square matrix, where n is an odd number, return the matrix without the central row and the central column.

2 months ago

Solved

MatCAT - Reconstruct X from Its X-rays
Consider a matrix x x = [ 1 2 0 0 5 0 3 0 8 ] If we sum x along the rows we get row_sums = [3 5 11] ...

2 months ago

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Given a matrix, swap the 2nd & 3rd columns
If a = [1 2 3 4; 1 2 3 4; 1 2 3 4; 1 2 3 4]; then the result is ans = 1 3 2 4 1 3 2...

2 months ago

Solved

matrix zigzag
Unfold a 2-D matrix to a 1-D array in zig-zag order, e.g., for matrix [ 1 2 3 ; 4 5 6 ; 7 8 9 ] the resulting 1-...

2 months ago

Solved

Determine the number of odd integers in a vector
Determine the number of unique odd integers in a vector. Examples: Input x = [2 5 8 3 7 1]; Output y = 4; Inp...

2 months ago

Solved

Reference Index Number
Given a reference set R of elements (each unique but identical in type), and a list V of elements drawn from the set R, possibly...

2 months ago