Data commit

Task/Smarandache-prime-digital-sequence/C/smarandache-prime-digital-sequence.c

@@ -0,0 +1,71 @@
+#include <locale.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+
+typedef uint32_t integer;
+
+integer next_prime_digit_number(integer n) {
+    if (n == 0)
+        return 2;
+    switch (n % 10) {
+    case 2:
+        return n + 1;
+    case 3:
+    case 5:
+        return n + 2;
+    default:
+        return 2 + next_prime_digit_number(n/10) * 10;
+    }
+}
+
+bool is_prime(integer n) {
+    if (n < 2)
+        return false;
+    if (n % 2 == 0)
+        return n == 2;
+    if (n % 3 == 0)
+        return n == 3;
+    if (n % 5 == 0)
+        return n == 5;
+    static const integer wheel[] = { 4,2,4,2,4,6,2,6 };
+    integer p = 7;
+    for (;;) {
+        for (int i = 0; i < 8; ++i) {
+            if (p * p > n)
+                return true;
+            if (n % p == 0)
+                return false;
+            p += wheel[i];
+        }
+    }
+}
+
+int main() {
+    setlocale(LC_ALL, "");
+    const integer limit = 1000000000;
+    integer n = 0, max = 0;
+    printf("First 25 SPDS primes:\n");
+    for (int i = 0; n < limit; ) {
+        n = next_prime_digit_number(n);
+        if (!is_prime(n))
+            continue;
+        if (i < 25) {
+            if (i > 0)
+                printf(" ");
+            printf("%'u", n);
+        }
+        else if (i == 25)
+            printf("\n");
+        ++i;
+        if (i == 100)
+            printf("Hundredth SPDS prime: %'u\n", n);
+        else if (i == 1000)
+            printf("Thousandth SPDS prime: %'u\n", n);
+        else if (i == 10000)
+            printf("Ten thousandth SPDS prime: %'u\n", n);
+        max = n;
+    }
+    printf("Largest SPDS prime less than %'u: %'u\n", limit, max);
+    return 0;
+}