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finding nth prime number
Nov 15, 2017 at 11:24pm
This program is supposed to be able to output the nth prime number. For example if the user enters "4" the program should output 7 because that is the fourth prime number.
Last edited on Nov 16, 2017 at 12:15am
Nov 15, 2017 at 11:44pm
Your IsPrime() isn’t simply unoptimal, it is flat out wrong. (Sorry.)
Consider using the Sieve of Eratosthenes algorithm. That is, build yourself a list of prime numbers: for each new number you wish to add to the list, only add it if none of the numbers currently in the list divide evenly into it; stop when your list is N primes long. (Yes, I’m advocating an n² algorithm.)
PS. You don't need globals.
Consider using the Sieve of Eratosthenes algorithm. That is, build yourself a list of prime numbers: for each new number you wish to add to the list, only add it if none of the numbers currently in the list divide evenly into it; stop when your list is N primes long. (Yes, I’m advocating an n² algorithm.)
PS. You don't need globals.
Last edited on Nov 15, 2017 at 11:46pm
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