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pe_027.cpp
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pe_027.cpp
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#include <iostream>
#include "timer.h"
/*/
Considering quadratics of the form:
n^2 + an + b, where |a|<1000 and |b|<1000
Find the product of the coefficients, a and b, for the quadratic expression
that produces the maximum number of primes for consecutive values of n,
starting with n=0.
/*/
bool isprime(int num) {
int i = 2, init=num;
if(!num) return false;
while(num % i == 0) {
num /= i;
}
if(num != 1) {
++i;
while(num > 1) {
while(num % i == 0) {
num /= i;
}
i+=2;
}
i-=2;
}
return i == init;
}
int main() {
int product;
const short CAP = 1000;
//attempt1 - bruteforce
{
product = 0;
short max = 0;
long n;
Timer t;
for(short a = -(CAP-1); a<CAP; a++) {
for(short b = -(CAP-1); b<CAP; b++) {
n = 0;
while(isprime(n*n + a*n + b))
++n;
if(n>max) {
max = n;
product = a*b;
}
}
}
}
std::cout<<product<<std::endl;
return 0;
}