The Collatz Conjecture or 3x+1 problem can be summarized as follows:
Take any positive integer n. If n is even, divide n by 2 to get n / 2. If n is odd, multiply n by 3 and add 1 to get 3n + 1. Repeat the process indefinitely. The conjecture states that no matter which number you start with, you will always reach 1 eventually.
Given a number n, return the number of steps required to reach 1.
Starting with n = 12, the steps would be as follows:
Resulting in 9 steps. So for input n = 12, the return value would be 9.
An unsolved problem in mathematics named after mathematician Lothar Collatz https://en.wikipedia.org/wiki/3x_%2B_1_problem
This exercise has been tested on Julia versions >=1.0.
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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# submit
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# canonical data version: 1.2.1
using Test
# include("collatz-conjecture.jl")
# canonical data
@test collatz_steps(1) == 0
@test collatz_steps(16) == 4
@test collatz_steps(12) == 9
@test collatz_steps(1000000) == 152
@test_throws DomainError collatz_steps(0)
@test_throws DomainError collatz_steps(-15)
To submit your exercise, you need to save your solution in a file called collatz-conjecture.jl before using the CLI.
You can either create it manually or use the following functions, which will automatically write every notebook cell that starts with # submit to the file collatz-conjecture.jl.
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# using Pkg; Pkg.add("Exercism")
# using Exercism
# Exercism.create_submission("collatz-conjecture")