Data commit

Task/Deceptive-numbers/C/deceptive-numbers.c

@@ -0,0 +1,36 @@
+#include <stdio.h>
+
+unsigned modpow(unsigned b, unsigned e, unsigned m)
+{
+    unsigned p;
+    for (p = 1; e; e >>= 1) {
+        if (e & 1)
+            p = p * b % m;
+        b = b * b % m;
+    }
+    return p;
+}
+
+int is_deceptive(unsigned n)
+{
+    unsigned x;
+    if (n & 1 && n % 3 && n % 5) {
+        for (x = 7; x * x <= n; x += 6) {
+            if (!(n % x && n % (x + 4)))
+                return modpow(10, n - 1, n) == 1;
+        }
+    }
+    return 0;
+}
+
+int main(void)
+{
+    unsigned c, i = 49;
+    for (c = 0; c != 50; ++i) {
+        if (is_deceptive(i)) {
+            printf(" %u", i);
+            ++c;
+        }
+    }
+    return 0;
+}