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Prime factor digits

Consider the following number system. Calculate the prime factorization for each number n, then represent the prime factors in a...

2 years ago

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Balanced number

Given a positive integer find whether it is a balanced number. For a balanced number the sum of first half of digits is equal to...

2 years ago

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Sums with Excluded Digits

Add all the integers from 1 to n in which the digit m does not appear. m will always be a single digit integer from 0 to 9. no...

2 years ago

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Find the longest sequence of 1's in a binary sequence.

Given a string such as s = '011110010000000100010111' find the length of the longest string of consecutive 1's. In this examp...

2 years ago

Problem

Vector of digits (★★)

Given a positive integer x, construct a vector y with all the digits of x in the order of appearance in x. Thus, if x = 172...

2 years ago | 0 | 47 solvers

Solved

Kaprekar Steps

6174 is the <http://en.wikipedia.org/wiki/6174_%28number%29 Kaprekar constant>. All natural numbers less than 10,000 (except som...

2 years ago

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The Goldbach Conjecture, Part 2

The <http://en.wikipedia.org/wiki/Goldbach's_conjecture Goldbach conjecture> asserts that every even integer greater than 2 can ...

2 years ago

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Counting Sequence

Given a vector x, find the "counting sequence" y. A counting sequence is formed by "counting" the entries in a given sequence...

2 years ago

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The Goldbach Conjecture

The <http://en.wikipedia.org/wiki/Goldbach's_conjecture Goldbach conjecture> asserts that every even integer greater than 2 can ...

2 years ago

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Making change

Given an amount of currency, return a vector of this form: [100 50 20 10 5 2 1 0.5 0.25 0.1 0.05 0.01] Example: Input a = ...

2 years ago

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Find the two most distant points

Given a collection of points, return the indices of the rows that contain the two points most distant from one another. The inpu...

2 years ago

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Maximum running product for a string of numbers

Given a string s representing a list of numbers, find the five consecutive numbers that multiply to form the largest number. Spe...

2 years ago

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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...

2 years ago

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Subset Sum

Given a vector v of integers and an integer n, return the the indices of v (as a row vector in ascending order) that sum to n. I...

2 years ago

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Which doors are open?

There are n doors in an alley. Initially they are all shut. You have been tasked to go down the alley n times, and open/shut the...

2 years ago

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Pascal's Triangle

Given an integer n >= 0, generate the length n+1 row vector representing the n-th row of <http://en.wikipedia.org/wiki/Pascals_t...

2 years ago

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Reverse Run-Length Encoder

Given a "counting sequence" vector x, construct the original sequence y. A counting sequence is formed by "counting" the entrie...

2 years ago

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Which values occur exactly three times?

Return a list of all values (sorted smallest to largest) that appear exactly three times in the input vector x. So if x = [1 2...

2 years ago

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Return a list sorted by number of occurrences

Given a vector x, return a vector y of the unique values in x sorted by the number of occurrences in x. Ties are resolved by a ...

2 years ago

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Return the 3n+1 sequence for n

A Collatz sequence is the sequence where, for a given number n, the next number in the sequence is either n/2 if the number is e...

2 years ago

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Bullseye Matrix

Given n (always odd), return output a that has concentric rings of the numbers 1 through (n+1)/2 around the center point. Exampl...

2 years ago

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Find all elements less than 0 or greater than 10 and replace them with NaN

Given an input vector x, find all elements of x less than 0 or greater than 10 and replace them with NaN. Example: Input ...

2 years ago

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Return the largest number that is adjacent to a zero

This example comes from Steve Eddins' blog: <http://blogs.mathworks.com/steve/2009/05/27/learning-lessons-from-a-one-liner/ Lear...

2 years ago

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Fibonacci sequence

Calculate the nth Fibonacci number. Given n, return f where f = fib(n) and f(1) = 1, f(2) = 1, f(3) = 2, ... Examples: Inpu...

2 years ago

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Tic Tac Toe FTW

Given a tic tac toe board: * 1 represents X * 0 represents empty. * -1 represents O It is X's move. If there is an imme...

2 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...

2 years ago

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Nearest Numbers

Given a row vector of numbers, find the indices of the two nearest numbers. Examples: [index1 index2] = nearestNumbers([2 5 3...

2 years ago

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Remove any row in which a NaN appears

Given the matrix A, return B in which all the rows that have one or more <http://www.mathworks.com/help/techdoc/ref/nan.html NaN...

2 years ago

Problem

Matrix indexing with two vectors of indices (★★)

(copy of Prob 589) Given a matrix M and two index vectors a and b, return a row vector x where x(i) = M(a(i),b(i)). Thus, if...

2 years ago | 0 | 31 solvers

Problem

Reindex a vector (★★)

(copy of Prob. 676) You are given two vectors of equal length. Vector N has numeric values (no Inf or NaN) while vector IDX h...

2 years ago | 0 | 37 solvers