1000 are Prime !

Computer Science Level 1

What is the sum of first 1000 prime numbers ?

3682933 3682943 3682923 3682913

Anish Harsha by Anish Harsha , 20, India

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4 solutions

Aryan Gaikwad
Feb 24, 2015

Java solution (try online - https://ideone.com/uTCwG4) - 

static int n = 1, sum = 2;
public static void main (String[] args) throws java.lang.Exception
{
    for(int i=2;;i++)
        if(isPrime(i)){
            sum += i;
            if(++n == 1000){
            System.out.println(sum);
            return;
            }
        }
}

static boolean isPrime(int n) {
    if (n%2==0) return false;
    for(int i=3;i*i<=n;i+=2)
        if(n%i==0) return false;
    return true;
}
0 Helpful 0 Interesting 0 Brilliant 0 Confused
Fox To-ong
Jan 29, 2015

since all the items were prime numbers up to 1000, the sum should be a prime number

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Rafael Nunes
Jan 3, 2015

I wrote a C++ algorithm to it, just look at: https://gist.github.com/rafaelcn/e5391bce91bcde61c135

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Brock Brown
Jan 2, 2015 
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from math import sqrt
def is_prime(x):
    if x < 2:
        return False
    i = 2
    while i <= sqrt(x):
        if x % i == 0:
            return False
        i+=1
    return True
primes = set()
i = 2
while len(primes) < 1000:
    if is_prime(i):
        primes.add(i)
    i += 1
print "Answer:", sum(primes)

0 Helpful 0 Interesting 0 Brilliant 0 Confused

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