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Challenges

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Challenges Is it stuck in a counting loop?

Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it (not necessarily contiguously). So f [1,1,2,2,1,3,3] = [1,2,1,2,3,1...

1 answer  ·  posted 1y ago by WheatWizard‭  ·  last activity 10mo ago by isaacg‭

#5: Post edited by user avatar trichoplax‭ · 2023-12-14T16:03:58Z (about 1 year ago)
Typo
Is it stuck in a counting loop?
  • Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it (not necessarily contiguously). So
  • ```
  • f [1,1,2,2,1,3,3] = [1,2,1,2,3,1,2]
  • ```
  • We will say that a list, $X$, is *in a loop* if there is some $n$ such that $f^n X = X$. That is you can apply the function to $X$ some number of times to arrive at $X$.
  • Your task is to take a loop as input and determine if that list is in a loop. You should output one of two consistent values, one if it is in a loop and the other if it is not.
  • This is code-golf. The goal is to minimize the size of your source code as measured in bytes.
  • ---
  • A note: There are other ways to formulate this condition.
  • ## Test cases
  • ```
  • [2,2] -> False
  • [1,1] -> True
  • [1,2] -> True
  • [1,1,2,2,3,3] -> True
  • [1,2,3,1,4,2,5,3] -> True
  • [1,2,1,3,1,2] -> True
  • [1,2,1,3,1,3,4,6] -> False
  • [1,2,2,3] -> False
  • ```
  • Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it (not necessarily contiguously). So
  • ```
  • f [1,1,2,2,1,3,3] = [1,2,1,2,3,1,2]
  • ```
  • We will say that a list, $X$, is *in a loop* if there is some positive integer $n$ such that $f^n X = X$. That is, you can apply the function to $X$ some number of times to arrive at $X$.
  • Your task is to take a list as input and determine if that list is in a loop. You should output one of two consistent values, one if it is in a loop and the other if it is not.
  • This is code-golf. The goal is to minimize the size of your source code as measured in bytes.
  • ---
  • A note: There are other ways to formulate this condition.
  • ## Test cases
  • ```
  • [2,2] -> False
  • [1,1] -> True
  • [1,2] -> True
  • [1,1,2,2,3,3] -> True
  • [1,2,3,1,4,2,5,3] -> True
  • [1,2,1,3,1,2] -> True
  • [1,2,1,3,1,3,4,6] -> False
  • [1,2,2,3] -> False
  • ```
#4: Post edited by user avatar WheatWizard‭ · 2023-12-14T15:35:57Z (about 1 year ago)
  • Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it. So
  • ```
  • f [1,1,2,2,1,3,3] = [1,2,1,2,3,1,2]
  • ```
  • We will say that a list, $X$, is *in a loop* if there is some $n$ such that $f^n X = X$. That is you can apply the function to $X$ some number of times to arrive at $X$.
  • Your task is to take a loop as input and determine if that list is in a loop. You should output one of two consistent values, one if it is in a loop and the other if it is not.
  • This is code-golf. The goal is to minimize the size of your source code as measured in bytes.
  • ---
  • A note: There are other ways to formulate this condition.
  • ## Test cases
  • ```
  • [2,2] -> False
  • [1,1] -> True
  • [1,2] -> True
  • [1,1,2,2,3,3] -> True
  • [1,2,3,1,4,2,5,3] -> True
  • [1,2,1,3,1,2] -> True
  • [1,2,1,3,1,3,4,6] -> False
  • [1,2,2,3] -> False
  • ```
  • Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it (not necessarily contiguously). So
  • ```
  • f [1,1,2,2,1,3,3] = [1,2,1,2,3,1,2]
  • ```
  • We will say that a list, $X$, is *in a loop* if there is some $n$ such that $f^n X = X$. That is you can apply the function to $X$ some number of times to arrive at $X$.
  • Your task is to take a loop as input and determine if that list is in a loop. You should output one of two consistent values, one if it is in a loop and the other if it is not.
  • This is code-golf. The goal is to minimize the size of your source code as measured in bytes.
  • ---
  • A note: There are other ways to formulate this condition.
  • ## Test cases
  • ```
  • [2,2] -> False
  • [1,1] -> True
  • [1,2] -> True
  • [1,1,2,2,3,3] -> True
  • [1,2,3,1,4,2,5,3] -> True
  • [1,2,1,3,1,2] -> True
  • [1,2,1,3,1,3,4,6] -> False
  • [1,2,2,3] -> False
  • ```
#3: Post edited by user avatar WheatWizard‭ · 2023-12-14T15:30:35Z (about 1 year ago)
  • Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it. So
  • ```
  • f [1,1,2,2,3,3] = [1,2,1,2,1,2]
  • ```
  • We will say that a list, $X$, is *in a loop* if there is some $n$ such that $f^n X = X$. That is you can apply the function to $X$ some number of times to arrive at $X$.
  • Your task is to take a loop as input and determine if that list is in a loop. You should output one of two consistent values, one if it is in a loop and the other if it is not.
  • This is code-golf. The goal is to minimize the size of your source code as measured in bytes.
  • ---
  • A note: There are other ways to formulate this condition.
  • ## Test cases
  • ```
  • [2,2] -> False
  • [1,1] -> True
  • [1,2] -> True
  • [1,1,2,2,3,3] -> True
  • [1,2,3,1,4,2,5,3] -> True
  • [1,2,1,3,1,2] -> True
  • [1,2,1,3,1,3,4,6] -> False
  • [1,2,2,3] -> False
  • ```
  • Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it. So
  • ```
  • f [1,1,2,2,1,3,3] = [1,2,1,2,3,1,2]
  • ```
  • We will say that a list, $X$, is *in a loop* if there is some $n$ such that $f^n X = X$. That is you can apply the function to $X$ some number of times to arrive at $X$.
  • Your task is to take a loop as input and determine if that list is in a loop. You should output one of two consistent values, one if it is in a loop and the other if it is not.
  • This is code-golf. The goal is to minimize the size of your source code as measured in bytes.
  • ---
  • A note: There are other ways to formulate this condition.
  • ## Test cases
  • ```
  • [2,2] -> False
  • [1,1] -> True
  • [1,2] -> True
  • [1,1,2,2,3,3] -> True
  • [1,2,3,1,4,2,5,3] -> True
  • [1,2,1,3,1,2] -> True
  • [1,2,1,3,1,3,4,6] -> False
  • [1,2,2,3] -> False
  • ```
#2: Post edited by user avatar WheatWizard‭ · 2023-12-14T15:00:33Z (about 1 year ago)
  • Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it. So
  • ```
  • f [1,1,2,2,3,3] = [1,2,1,2,1,2]
  • ```
  • We will say that a list, $X$, is *in a loop* if there is some $n$ such that $f^n X = X$. That is you can apply the function to $X$ some number of times to arrive at $X$.
  • Your task is to take a loop as input and determine if that list is in a loop. You should output one of two consistent values, one if it is in a loop and the other if it is not.
  • This is code-golf. The goal is to minimize the size of your source code as measured in bytes.
  • ## Test cases
  • ```
  • [2,2] -> False
  • [1,1] -> True
  • [1,2] -> True
  • [1,1,2,2,3,3] -> True
  • [1,2,3,1,4,2,5,3] -> True
  • [1,2,1,3,1,2] -> True
  • [1,2,1,3,1,3,4,6] -> False
  • [1,2,2,3] -> False
  • ```
  • Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it. So
  • ```
  • f [1,1,2,2,3,3] = [1,2,1,2,1,2]
  • ```
  • We will say that a list, $X$, is *in a loop* if there is some $n$ such that $f^n X = X$. That is you can apply the function to $X$ some number of times to arrive at $X$.
  • Your task is to take a loop as input and determine if that list is in a loop. You should output one of two consistent values, one if it is in a loop and the other if it is not.
  • This is code-golf. The goal is to minimize the size of your source code as measured in bytes.
  • ---
  • A note: There are other ways to formulate this condition.
  • ## Test cases
  • ```
  • [2,2] -> False
  • [1,1] -> True
  • [1,2] -> True
  • [1,1,2,2,3,3] -> True
  • [1,2,3,1,4,2,5,3] -> True
  • [1,2,1,3,1,2] -> True
  • [1,2,1,3,1,3,4,6] -> False
  • [1,2,2,3] -> False
  • ```
#1: Initial revision by user avatar WheatWizard‭ · 2023-12-14T14:56:41Z (about 1 year ago)
Is it stuck in a counting loop?
Given a list of non-negative integers the function $f$ replaces every integer with the number of identical integers preceding it. So

```
f [1,1,2,2,3,3] = [1,2,1,2,1,2]
```

We will say that a list, $X$, is *in a loop* if there is some $n$ such that $f^n X = X$.  That is you can apply the function to $X$ some number of times to arrive at $X$.

Your task is to take a loop as input and determine if that list is in a loop. You should output one of two consistent values, one if it is in a loop and the other if it is not.

This is code-golf. The goal is to minimize the size of your source code as measured in bytes.

## Test cases

```
[2,2] -> False
[1,1] -> True
[1,2] -> True
[1,1,2,2,3,3] -> True
[1,2,3,1,4,2,5,3] -> True
[1,2,1,3,1,2] -> True
[1,2,1,3,1,3,4,6] -> False
[1,2,2,3] -> False
```