Project Euler: http://projecteuler.net/

ProjectEuler/p010_SummationOfPrimes.cpp

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+/* Check cf5-opt.vim defs.
+VIM: let g:lcppflags="-std=c++11 -O2 -pthread"
+VIM: let g:wcppflags="/O2 /EHsc /DWIN32"
+*/
+#include <iostream>
+#include <vector>
+
+/*
+Summation of primes
+Problem 10
+
+The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
+
+Find the sum of all the primes below two million.
+
+Solution:
+142913828922
+*/
+typedef std::vector<long long> pt;
+pt p;
+
+bool isPrime( long long n )
+{
+	long h = (long long)sqrt(double(n));
+	for ( pt::iterator i = p.begin(), ie = p.end(); 
+			i!=ie && *i<=h;
+			++i )
+		if ( !(n%*i) )
+			return false;
+	return true;
+}
+
+int main ( void )
+{
+	const long long n = 2000000;
+	long long s = 0;
+
+	for ( long long i = 2; i < n; ++ i )
+		if ( isPrime( i ) )
+		{
+		   	p.push_back( i );
+		   	s+=i;
+		}
+	std::cout << s << std::endl;
+
+	return 0;
+}
+