[Algorithm/C] Project Euler. Summation of primes
Summaion_of_primes.cClick to download.
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
Find the sum of all the primes below two million.
/*
https://projecteuler.net/problem=10
Summation of primes
Writer : Mun Jae In
Date : 2017.12.15
*/
#include <stdio.h>
#include <math.h>
int isPrime(int n)
{
if(n==1)
{
return 0;
}
else if(n<4)
{
return 1;
}
else if(n%2==0)
{
return 0;
}
else if(n<9)
{
return 1;
}
else if(n%3==0)
{
return 0;
}
else
{
double r = floor(sqrt((double)n));
int f = 5;
while (f<=r)
{
if(n%f==0)
{
return 0;
}
else if(n%(f+2)==0)
{
return 0;
}
f += 6;
}
return 1;
}
}
int main(int argc, char * argv[])
{
int candidate = 1;
long long sum=0;
while(1)
{
candidate += 1;
if(isPrime(candidate))
{
sum += candidate;
}
if(candidate>=2000000) break;
}
printf("candidate : %d\n",candidate);
printf("sum : %lld\n",sum);
}
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