Project-Euler/euler.cpp at master · jdo227/Project-Euler · GitHub

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//P7:10001st prime

#include <iostream>
#include <math.h>
using namespace std;

bool isPrime(int n){
    if(n==1){
        return false;
    }
    else if(n<4){return true;}
    else if(n%2==0){return false;}
    else if(n<9){return true;}
    else if(n%3==0){return false;}
    else{
        int r=floor(sqrt(n));
        int f=5;
        while(f<=r){
            if(n%f==0){return false; break;}
            if(n%(f+2)==0){return false; break;}
            f+=6;
        }
        return true;
    }
}
int main() {
    int limit = 10001;
    int count = 1;
    int candidate = 1;
    do {
        candidate+=2;
        if(isPrime(candidate)){
            count++;
        }
    } while (count<limit);
    cout<<candidate<<'\n';
	return 0;
}