# 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
vector<long long int> readFile()
{
    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


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://maksimdan.gitbook.io/interview-practice-problems/project_eular/10_summation_of_primes.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.