Add problem 46 solution

primes.h

@@ -0,0 +1,21 @@
+int is_prime(long num)
+{
+	int i = 5;
+	int w = 2;
+
+	if (num == 1)
+		return 0;
+	if (num == 2 || num == 3)
+		return 1;
+	if (!(num%2) || !(num%3))
+		return 0;
+
+	while ((i*i) <= num) {
+		if (!(num%i))
+			return 0;
+		i += w;
+		w = 6 - w;
+	}
+
+	return 1;
+}

problem-46.c

@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include "primes.h"
+
+int next_prime(int num)
+{
+	num++;
+	while (1)
+		if (is_prime(num)) {
+			return num;
+		} else {
+			num++;
+		}
+}
+
+int check(int num)
+{
+	int i;
+	int prime = 2;
+
+	while (prime < num) {
+		for (i=1; i<(num-prime+1); i++)
+			if (num == prime+2*(i*i))
+				return 1;
+		prime = next_prime(prime);
+	}
+
+	return 0;
+}
+
+
+int main(int argc, char** argv)
+{
+	int i = 9; /* First odd composite */
+	while (1) {
+		if (!(check(i)))
+			break;
+
+		do {
+			i += 2;
+		} while (is_prime(i));
+	}
+
+	printf("The solution is %d\n", i);
+	return 0;
+}