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# Petr

85 total contributions since 2012

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sum of non-primes
The sum of the non-primes below 10 is 1+4+6+8+9+10=38 Find the sum of all the non-primes below the input, N.

4 years ago

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Find max
Find the maximum value of a given vector or matrix.

4 years ago

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Project Euler: Problem 10, Sum of Primes
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below the input, N. Thank you <http:/...

4 years ago

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First N Perfect Squares
*Description* Return the first N perfect squares *Example* input = 4; output = [ 1 4 9 16 ];

4 years ago

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Set a diagonal
Given a matrix M, row vector v of appropriate length, and diagonal index d (where 0 indicates the main diagonal and off-diagonal...

4 years ago

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We love vectorized solutions. Problem 1 : remove the row average.
Given a 2-d matrix, remove the row average from each row. Your solution MUST be vectorized. The solution will be tested for ac...

4 years ago

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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...

4 years ago

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Unique values without using UNIQUE function
You must return unique values in a vector in *stable* mode without using the unique function. About stable order flag: ...

4 years ago

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Back to basics 9 - Indexed References
Covering some basic topics I haven't seen elsewhere on Cody. Given an input matrix and row and column, output the index of th...

4 years ago

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"mirror" matrix
Create n x 2n "mirror" matrix of this type: e.g. for n = 2 m = [1 2 2 1;1 2 2 1] e.g. for n = 3 m = [1 2 3 3 2 1...

4 years ago

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Target sorting
Sort the given list of numbers |a| according to how far away each element is from the target value |t|. The result should return...

4 years ago

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Tricky timing
Write a function that takes between 0.5 seconds and 0.6 seconds to run.

4 years ago

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Back to basics 23 - Triangular matrix
Covering some basic topics I haven't seen elsewhere on Cody. Given an input matrix, return a matrix with all elements above a...

4 years ago

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Back to basics 11 - Max Integer
Covering some basic topics I haven't seen elsewhere on Cody. Return the largest positive integer MATLAB can handle.

4 years ago

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Back to basics 10 - Max Float
Covering some basic topics I haven't seen elsewhere on Cody. Return the largest positive floating-point number MATLAB can han...

4 years ago

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All your base are belong to us
Find the base _b_ logarithm of the input decimal number _x_. Express the output as a decimal number. The first argument is the n...

4 years ago

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Quote Doubler
Given a string s1, find all occurrences of the single quote character and replace them with two occurrences of the single quote ...

4 years ago

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Remove the vowels
Remove all the vowels in the given phrase. Example: Input s1 = 'Jack and Jill went up the hill' Output s2 is 'Jck nd Jll wn...

4 years ago

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Sophie Germain prime
In number theory, a prime number p is a *Sophie Germain prime* if 2p + 1 is also prime. For example, 23 is a Sophie Germain prim...

4 years ago

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Sum of diagonal of a square matrix
If x = [1 2 4; 3 4 5; 5 6 7] then y should be the sum of the diagonals of the matrix y = 1 + 4 + 7 = 12

4 years ago

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Back to basics 22 - Rotate a matrix
Covering some basic topics I haven't seen elsewhere on Cody. Rotate the input matrix 90 degrees counterclockwise (e.g. [1 2; ...

4 years ago

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Remove NaN ?
input -> matrix (n*m) with at least one element equal to NaN; output -> matrix(p*m), the same matrix where we deleted the enti...

4 years ago

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So many choices
For inputs _n_ and _k_ (in that order), output the number of ways that k objects can be chosen from amongst n distinct objects. ...

4 years ago

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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...

4 years ago

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Factorize THIS, buddy
List the prime factors for the input number, in decreasing order. List each factor only once, even if the factorization includes...

4 years ago

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Roll the Dice!
*Description* Return two random integers between 1 and 6, inclusive, to simulate rolling 2 dice. *Example* [x1,x2] =...

4 years ago

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Distance walked 1D
Suppose you go from position 7 to 10 to 6 to 4. Then you have walked 9 units of distance, since 7 to 10 is 3 units, 10 to 6 is 4...

4 years ago

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Too mean-spirited
Find the mean of each consecutive pair of numbers in the input row vector. For example, x=[1 2 3] ----> y = [1.5 2.5] x=[1...

4 years ago

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Create times-tables
At one time or another, we all had to memorize boring times tables. 5 times 5 is 25. 5 times 6 is 30. 12 times 12 is way more th...

4 years ago

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Most nonzero elements in row
Given the matrix a, return the index r of the row with the most nonzero elements. Assume there will always be exactly one row th...

4 years ago