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exercises/practice/collatz-conjecture/.docs/instructions.md
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# Instructions | ||
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The Collatz Conjecture or 3x+1 problem can be summarized as follows: | ||
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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. | ||
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Given a number n, return the number of steps required to reach 1. | ||
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## Examples | ||
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Starting with n = 12, the steps would be as follows: | ||
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0. 12 | ||
1. 6 | ||
2. 3 | ||
3. 10 | ||
4. 5 | ||
5. 16 | ||
6. 8 | ||
7. 4 | ||
8. 2 | ||
9. 1 | ||
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Resulting in 9 steps. | ||
So for input n = 12, the return value would be 9. | ||
Given a positive integer, return the number of steps it takes to reach 1 according to the rules of the Collatz Conjecture. |
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exercises/practice/collatz-conjecture/.docs/introduction.md
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# Introduction | ||
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One evening, you stumbled upon an old notebook filled with cryptic scribbles, as though someone had been obsessively chasing an idea. | ||
On one page, a single question stood out: **Can every number find its way to 1?** | ||
It was tied to something called the **Collatz Conjecture**, a puzzle that has baffled thinkers for decades. | ||
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The rules were deceptively simple. | ||
Pick any positive integer. | ||
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- If it's even, divide it by 2. | ||
- If it's odd, multiply it by 3 and add 1. | ||
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Then, repeat these steps with the result, continuing indefinitely. | ||
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Curious, you picked number 12 to test and began the journey: | ||
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12 ➜ 6 ➜ 3 ➜ 10 ➜ 5 ➜ 16 ➜ 8 ➜ 4 ➜ 2 ➜ 1 | ||
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Counting from the second number (6), it took 9 steps to reach 1, and each time the rules repeated, the number kept changing. | ||
At first, the sequence seemed unpredictable — jumping up, down, and all over. | ||
Yet, the conjecture claims that no matter the starting number, we'll always end at 1. | ||
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It was fascinating, but also puzzling. | ||
Why does this always seem to work? | ||
Could there be a number where the process breaks down, looping forever or escaping into infinity? | ||
The notebook suggested solving this could reveal something profound — and with it, fame, [fortune][collatz-prize], and a place in history awaits whoever could unlock its secrets. | ||
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[collatz-prize]: https://mathprize.net/posts/collatz-conjecture/ |
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# Introduction | ||
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Your body is made up of cells that contain DNA. | ||
Those cells regularly wear out and need replacing, which they achieve by dividing into daughter cells. | ||
In fact, the average human body experiences about 10 quadrillion cell divisions in a lifetime! | ||
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When cells divide, their DNA replicates too. | ||
Sometimes during this process mistakes happen and single pieces of DNA get encoded with the incorrect information. | ||
If we compare two strands of DNA and count the differences between them, we can see how many mistakes occurred. | ||
This is known as the "Hamming distance". | ||
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The Hamming distance is useful in many areas of science, not just biology, so it's a nice phrase to be familiar with :) |
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# Introduction | ||
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At the Global Verification Authority, you've just been entrusted with a critical assignment. | ||
Across the city, from online purchases to secure logins, countless operations rely on the accuracy of numerical identifiers like credit card numbers, bank account numbers, transaction codes, and tracking IDs. | ||
The Luhn algorithm is a simple checksum formula used to ensure these numbers are valid and error-free. | ||
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A batch of identifiers has just arrived on your desk. | ||
All of them must pass the Luhn test to ensure they're legitimate. | ||
If any fail, they'll be flagged as invalid, preventing errors or fraud, such as incorrect transactions or unauthorized access. | ||
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Can you ensure this is done right? The integrity of many services depends on you. |
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