Initial data commit

Task/Additive-primes/C/additive-primes.c

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+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+void memoizeIsPrime( bool * result, const int N )
+{
+    result[2] = true;
+    result[3] = true;
+    int prime[N];
+    prime[0] = 3;
+    int end = 1;
+    for (int n = 5; n < N; n += 2)
+    {
+        bool n_is_prime = true;
+        for (int i = 0; i < end; ++i)
+        {
+            const int PRIME = prime[i];
+            if (n % PRIME == 0)
+            {
+                n_is_prime = false;
+                break;
+            }
+            if (PRIME * PRIME > n)
+            {
+                break;
+            }
+        }
+        if (n_is_prime)
+        {
+            prime[end++] = n;
+            result[n] = true;
+        }
+    }
+}/* memoizeIsPrime */
+
+int sumOfDecimalDigits( int n )
+{
+    int sum = 0;
+    while (n > 0)
+    {
+        sum += n % 10;
+        n /= 10;
+    }
+    return sum;
+}/* sumOfDecimalDigits */
+
+int main( void )
+{
+    const int N = 500;
+
+    printf( "Rosetta Code: additive primes less than %d:\n", N );
+
+    bool is_prime[N];
+    memset( is_prime, 0, sizeof(is_prime) );
+    memoizeIsPrime( is_prime, N );
+
+    printf( "   2" );
+    int count = 1;
+    for (int i = 3; i < N; i += 2)
+    {
+        if (is_prime[i] && is_prime[sumOfDecimalDigits( i )])
+        {
+            printf( "%4d", i );
+            ++count;
+            if ((count % 10) == 0)
+            {
+                printf( "\n" );
+            }
+        }
+    }
+    printf( "\nThose were %d additive primes.\n", count );
+    return 0;
+}/* main */