Project Euler Problem 7
I mentioned yesterday, I’ve been doing the first few problems of Project Euler and figured I’d share my solution to problem 7 here.
The Problem
By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.
What is the 10,001st prime number?
The Solution
Let’s define a function isPrime(num) (granted, could be more efficient) and loop through the natural numbers, counting those that are prime.
/** * Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum. **/ #include using namespace std; bool isPrime ( unsigned long num ) { for(int i = num - 1; i > 1; i--) { if(num % i == 0) { return false; } } return true; } int main () { unsigned long num = 2, primeCount = 0; while ( primeCount < 10001 ) { if ( isPrime (num) ) { primeCount++; cout << "Prime " << primeCount << " " << num << " is prime" << endl; } num++; } return(0); }
