Correct answer will not output
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by rEgonicS
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Published on 2010-05-10T04:07:32Z
Indexed on
2010/05/10
4:18 UTC
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I made a program that returns the sum of all primes under 2 million. I really have no idea what's going on with this one, I get 142891895587 as my answer when the correct answer is 142913828922. It seems like its missing a few primes in there. I'm pretty sure the getPrime function works as it is supposed to. I used it a couple times before and worked correctly than. The code is as follows:
vector<int> getPrimes(int number);
int main()
{
unsigned long int sum = 0;
vector<int> primes = getPrimes(2000000);
for(int i = 0; i < primes.size(); i++)
{
sum += primes[i];
}
cout << sum;
return 0;
}
vector<int> getPrimes(int number)
{
vector<bool> sieve(number+1,false);
vector<int> primes;
sieve[0] = true;
sieve[1] = true;
for(int i = 2; i <= number; i++)
{
if(sieve[i]==false)
{
primes.push_back(i);
unsigned long int temp = i*i;
while(temp <= number)
{
sieve[temp] = true;
temp = temp + i;
}
}
}
return primes;
}
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