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Combinations without using nchoosek
You have to generate a matrix with all possible combinations of n elements *taken 2* at a time, *without using nchoosek(1:n,2)* ...

1 year ago

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Which permutation is it?
Let write some permutations of positive integers. 1: 1 2 3 4 5 6 ... 2: 2 1 3 4 ... 3: 1 3 2 4 ....

1 year ago

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N-th permutation.
Let write some permutations of positive integers. 1: 1 2 3 4 5 6 ... 2: 2 1 3 4 ... 3: 1 3 2 4 ... ...

1 year ago

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Diophantine Equations (Inspired by Project Euler, problem 66)
Consider the quadratic Diophantine equation of the form: x^2 – Dy^2 = 1 When D=13, the minimal solution in x is 649^2 – 13...

1 year ago

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High Precision Square Root (Inspired by Project Euler 80)
Given a positive integer n which is not a perfect square, write a MATLAB script that will calculate the square root of n truncat...

1 year ago

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Decrypt the cypher using XOR encryption (for beginners)
Inspired by Project Euler n°59 Each character on a computer is assigned a unique code and the preferred standard is ASCII (...

1 year ago

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I've got the power! (Inspired by Project Euler problem 29)
Consider all integer combinations of a^b and b^a for the integer values 2 ≤ a ≤ 4 and 2 ≤ b ≤ 5: 2^2=4, 2^3=8, 2^4=16,...

1 year ago

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Repopulate the City
For any population p of positive integers between pmin and pmax, we can calculate histogram count n for a list of evenly dividin...

1 year ago

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Compute the Lagarias Riemann Hypothesis sequence
Write a function that takes an input number and produces a sequence (i.e., all values up to and including the th value) compute...

1 year ago

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Compute the unitary totient of a number
The totient function , the subject of Cody Problems 656 and 50182, gives the number of integers smaller than that are relativel...

1 year ago

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List the nth term of Rozhenko’s inventory sequence
Consider a sequence constructed by repeated inventories. A new inventory begins each time a zero is encountered. The first few i...

1 year ago

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Count estrangements
Recently I made a puzzle for my wife that included a cryptogram, which involves an arrangement of the letters A through Z. I use...

1 year ago

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Trap a knight
Consider a knight on an infinite chessboard labeled with numbers spiraling outward. A knight starting on the square labeled 1 ca...

1 year ago

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Compute the Tetris sequence
In the Tetris sequence, which starts with a 1, the next term is the smallest positive integer not already in the sequence that h...

1 year ago

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Flip the parity of digits in a decimal expansion
The number 349 has the decimal expansion . If we change the even digits from positive to negative, then the number becomes 269 (...

1 year ago

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Compute the largest number with a given integer complexity
Cody Problems 42831 and 42834 ask us to compute integer complexity, the smallest number of 1s needed to construct a number with ...

1 year ago

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Sum the unitary divisors of a number
Cody Problems 1933 and 46898 deal with , the sum of divisors function. This problem deals with , the sum of unitary divisors fun...

1 year ago

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Count the unitary divisors of a number
Cody Problem 56738 asks for a list of the unitary divisors of a number. For this problem, write a function to count the unitary ...

1 year ago

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List numbers that are not squares
The numbers 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 17, etc. are not perfect squares. Write a function to list the th term in ...

1 year ago

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Count the peaceful queens
In a 5x5 chessboard with a queen of one color (white, say) on the perimeter, one can place 12 black queens on the board such tha...

1 year ago

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Generate the Figure-Figure sequence
After discussing Scott Kim’s FIGURE-FIGURE Figure (below) in Gödel, Escher, Bach, Douglas Hofstadter introduced an integer seque...

1 year ago

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Determine whether the input is an anagram number
In Cody Problem 44293, Mehmet OZC asks us to spell numbers as words. For example, 67 would be “sixty-seven” and 76 would be “sev...

1 year ago

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Compute a determinant
Write a function to compute the determinant of an x matrix with diagonal entries equal to an integer and other entries equal ...

1 year ago

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The sliding puzzle: 3D
This is an extension of problem 42842. In this case, the puzzle is three-dimensional and is of size 3x3x3. Of the 27 positions i...

2 years ago

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Tautology
Check if the given expression is always true. For example, the sentence '~(A & B) == (~A | ~B)' is always true. Chara...

2 years ago

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Is this a valid Tic Tac Toe State?
For the game of <https://en.wikipedia.org/wiki/Tic-tac-toe Tic Tac Toe> we will be storing the state of the game in a matrix M. ...

2 years ago

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Hexagonal numbers on a spiral matrix
Put hexagonal numbers in a ( m x m ) spiral matrix and return the sum of its diagonal elements. Formula of hexagonal numbers ...

2 years ago

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Digit concentration in Champernowne's constant
Consider the first 50 digits of Champernowne's constant 0.12345678910111213141516171819202122232425262728293... The...

2 years ago

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Ned's queens
A tribute to Cody's five-year anniversary should also celebrate the people behind Cody, and in this particular case, our illustr...

2 years ago

Solved

Acid and water
⚖ ⚖ ⚖ ⚖ ⚖ ⚖ ⚖ ⚖ Assume that there is a 100 liter tank. It is initially fi...

2 years ago