# 10 Summation of Primes

The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.

Find the sum of all the primes below two million.

``````#include <iostream>
#include <fstream>
#include <limits>
#include <vector>

using namespace std;

void pause() { cin.ignore(numeric_limits<streamsize>::max(), '\n'); }

// This function is incredibly slow
bool checkIfPrime(int number)
{
long int count = 2;
for (int j = 2; j <= number - 1; j++)
{
// 2) Check if actually prime
if (number % j == 0)
{
return false;
}

else if (count == number - 1)
{
return true;
}
count++;
}
}

// Method 2: Reading from a list of prime numbers
{
ifstream inFile;
inFile.open("primes1.txt");

if (inFile.fail())
{
cerr << "Error opening file";
exit(1);
}
vector <long long int> primes;
long long int prime;

while (inFile >> prime)
{
primes.push_back(prime);
}

return primes;
}

int main()
{
vector <long long int> thePrimes = readFile();

int count = 0;
long long int sum = 0;
int number = 2000000;

while (true)
{
if (thePrimes[count] <= number)
{
sum += thePrimes[count];
count++;
}

else
break;
}

cout << sum;
pause();
}``````

My biggest setback here was learning how to read files with visual studio. After a while, I have realized that it was nessessary to place your specific file in the directory folder, as well as add it in the resource files of VS.

Solution: 142913828922

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