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Problem 2: Finding Primes

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Problem 2: Finding Primes Empty Problem 2: Finding Primes

Post  Elusive Sat Jun 04, 2011 3:43 pm

What is a prime number, specified by order?

Inputs: Which prime number to return, e.g. 1st, 8th, etc. Will be supplied as an integer.
Outputs: Prime number, specified by input.

Example:
Code:

1st prime num: 2
Code:

50th prime num: 229
Code:

10000th prime num: 104729

Tips:
  1. Wikipedia wrote:A prime number (or a prime) is a natural number that has exactly two distinct natural number divisors: 1 and itself.
    Therefore, 1 is not a prime number, and 2 is the first prime number.
  2. Don't use an online prime generator, that won't help you learn to code one.
  3. You can use an online prime checker to make sure the numbers your program returns are prime.
  4. Arrays in C based languages are zero-indexed (start at 0), while the number specified will be indexed at one (starts at 1). Remember that if you are using one.
  5. Numbers above one million could take some time to find, so it is best to perform tests with smaller numbers.
  6. This can be solved recursively or in a loop, I personally used a loop for simplicity.
  7. If trial division (dividing by every number below it) is too slow, here are a few ways to speed it up:
    1. Spoiler:
    2. Spoiler:
    3. Spoiler:

Elusive
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Posts : 10
Join date : 2011-06-04

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