How to Generate the First N Prime Numbers

How do you find the first N prime numbers in python?

You only increment min in the else block, i.e., if min % c is nonzero for all c, i.e., if min is prime. This means that the code won't be able to move past any composite numbers. You can fix this by unindenting min=min+1 one level so that it lines up with the for and else.

How do I generate the first n prime numbers?

In Ruby 1.9 there is a Prime class you can use to generate prime numbers, or to test if a number is prime:

require 'prime'

Prime.take(10) #=> [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
Prime.take_while {|p| p < 10 } #=> [2, 3, 5, 7]
Prime.prime?(19) #=> true

Prime implements the each method and includes the Enumerable module, so you can do all sorts of fun stuff like filtering, mapping, and so on.

How to create a loop that returns the first N prime numbers in a vector?

You could write a recursive function (a function that calls itself). In addition to the two arguments n and all, it would also take a counter i and a (empty) vector of prime numbers primes.

As long as the number of prime numbers found is less than n, the function calls itself and with each time it calls itself, it would increase the counter variable i. If i is a prime number, it gets added to the primes vector.

get_prime <- function(n, all = TRUE, i = 1, primes = c()){
  if ( n <= 0) {
    stop("Not a valid number")
  }

  if (length(primes) < n) {
    if (i == 2L || all(i %% 2L:ceiling(sqrt(i)) != 0)) {
      get_prime(n, all = all, i = i + 1, primes = c(primes, i))
    } else {
      get_prime(n, all = all, i = i + 1, primes = primes)
    }
  } else {
    if (all) {
      return(primes)
    } else {
      return(tail(primes, 1))
    }
  }
}

The results are:

get_prime(7, TRUE)
[1]  2  3  5  7 11 13 17
get_prime(7, FALSE)
[1] 17

Sieve of Eratosthenes for first n prime numbers

You should count only prime numbers, not all numbers.

Also the range of i for looping should be corrected. The first prime number is 2 and the element arr[100] is not available.

for (int i = 2, count = 0; i < 100 && count != n; i++) // don't increment count here
{
    if (arr[i] == 0)
    {
        cout << i << '\n';
        count++; // count a prime number here
    }
}

Python program to store first N prime numbers in a list?

This will return array of count primes:

def get_primes(count):
    primes = []

    n = 2
    while len(primes) != count:
        for i in range(2, n // 2 + 1):
            if n % i == 0:
                break
        else:
            primes.append(n)
        n += 1

    return primes

you can use it like so:

n=input("Enter the number of prime numbers to be displayed: ")
array_of_n_prime_numbers = get_primes(n)
print("The prime numbers are:", array_of_n_prime_numbers)

---

Related Topics