euler39.c


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#include <stdio.h>

int np(int p)
{
	int n = 0;
	int a;

	/* p = a + b + c, with a*a+b*b=c*c */
	/* b = (p*p-2pa)/(2p-2a) */
	if (p % 2 == 1)
		return 0;

	a = 1;
	while (1) {
		int nu = p * (p - a*2);
		int de = (p - a) * 2;
		if (nu % de == 0 && nu/de > a)
			n++;
		if (nu/de < a)
			break;
		a++;
	}
	return n;
}

int main()
{
	int bestp, M = 0;
	int i;
	for (i = 3; i<=1000; i++) {
		int m = np(i);
		if (m > M) {
			bestp = i;
			M = m;
		}
	}
	printf("%d\n", bestp);
}