nth prime

Write a method that returns the ‘n’th prime number. Recall that only numbers greater than 1 can be prime.

nth_prime(1) == 2
nth_prime(2) == 3
nth_prime(3) == 5
nth_prime(4) == 7
nth_prime(5) == 11

Use previous ‘is_prime?’ solution.

screen-shot-2016-09-20-at-4-31-36-pm

screen-shot-2016-09-20-at-4-41-39-pm

Thought process:

  • First, start with i = 2 and check to see if it’s a prime number.
  • If it’s a prime number, which 2 is, increment the nth_num to 1.  (This sets nth_prime(1) == 2.)
  • If it’s not a prime number, nothing will happen and it won’t be given an nth_number.  Instead, the program will increment i to check if the next number is a prime number.
  • Finally, if nth_num is the same as the input argument (n), then the program will spit out i, which is the prime number set for that nth.
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nth prime

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