Data commit

Task/Attractive-numbers/C/attractive-numbers.c

@@ -0,0 +1,51 @@
+#include <stdio.h>
+
+#define TRUE 1
+#define FALSE 0
+#define MAX 120
+
+typedef int bool;
+
+bool is_prime(int n) {
+    int d = 5;
+    if (n < 2) return FALSE;
+    if (!(n % 2)) return n == 2;
+    if (!(n % 3)) return n == 3;
+    while (d *d <= n) {
+        if (!(n % d)) return FALSE;
+        d += 2;
+        if (!(n % d)) return FALSE;
+        d += 4;
+    }
+    return TRUE;
+}
+
+int count_prime_factors(int n) {
+    int count = 0, f = 2;
+    if (n == 1) return 0;
+    if (is_prime(n)) return 1;
+    while (TRUE) {
+        if (!(n % f)) {
+            count++;
+            n /= f;
+            if (n == 1) return count;
+            if (is_prime(n)) f = n;
+        }
+        else if (f >= 3) f += 2;
+        else f = 3;
+    }
+}
+
+int main() {
+    int i, n, count = 0;
+    printf("The attractive numbers up to and including %d are:\n", MAX);
+    for (i = 1; i <= MAX; ++i) {
+        n = count_prime_factors(i);
+        if (is_prime(n)) {
+            printf("%4d", i);
+            if (!(++count % 20)) printf("\n");
+        }
+    }
+    printf("\n");
+    return 0;
+}