Data commit

Task/Vampire-number/C/vampire-number.c

@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <math.h>
+
+typedef uint64_t xint;
+typedef unsigned long long ull;
+
+xint tens[20];
+
+inline xint max(xint a, xint b) { return a > b ? a : b; }
+inline xint min(xint a, xint b) { return a < b ? a : b; }
+inline int ndigits(xint x)
+{
+	int n = 0;
+	while (x) n++, x /= 10;
+	return n;
+}
+
+inline xint dtally(xint x)
+{
+	xint t = 0;
+	while (x) t += 1<<((x%10) * 6), x /= 10;
+
+	return t;
+}
+
+int fangs(xint x, xint *f)
+{
+	int n = 0;
+	int nd = ndigits(x);
+	if (nd & 1) return 0;
+	nd /= 2;
+
+	xint lo, hi;
+	lo = max(tens[nd-1], (x + tens[nd] - 2)/ (tens[nd] - 1));
+	hi = min(x / lo, sqrt(x));
+
+	xint a, b, t = dtally(x);
+	for (a = lo; a <= hi; a++) {
+		b = x / a;
+		if (a * b == x && ((a%10) || (b%10)) && t == dtally(a) + dtally(b))
+			f[n++] = a;
+	}
+
+	return n;
+}
+
+void show_fangs(xint x, xint *f, xint cnt)
+{
+	printf("%llu", (ull)x);
+	int i;
+	for (i = 0; i < cnt; i++)
+		printf(" = %llu x %llu", (ull)f[i], (ull)(x / f[i]));
+	putchar('\n');
+}
+
+int main(void)
+{
+	int i, j, n;
+	xint x, f[16], bigs[] = {16758243290880ULL, 24959017348650ULL, 14593825548650ULL, 0};
+
+	tens[0] = 1;
+	for (i = 1; i < 20; i++)
+		tens[i] = tens[i-1] * 10;
+
+	for (x = 1, n = 0; n < 25; x++) {
+		if (!(j = fangs(x, f))) continue;
+		printf("%2d: ", ++n);
+		show_fangs(x, f, j);
+	}
+
+	putchar('\n');
+	for (i = 0; bigs[i]; i++) {
+		if ((j = fangs(bigs[i], f)))
+			show_fangs(bigs[i], f, j);
+		else
+			printf("%llu is not vampiric\n", (ull)bigs[i]);
+	}
+
+	return 0;
+}