projecteuler solution 187

1 files changed, 30 insertions, 0 deletions

diff --git a/src/projecteuler/187.c b/src/projecteuler/187.c
new file mode 100644
index 0000000..a2e552e
--- /dev/null
+++ b/src/projecteuler/187.c
@@ -0,0 +1,30 @@
+#include "common.h"
+#include <stdlib.h>
+#include <string.h>
+
+// TODO: works only on 64 bit systems
+
+const unsigned long limit = 100000000;
+
+int main(void)
+{
+	unsigned long* p = primes(limit/2); // sqrt(limit)
+	unsigned long pcount = p[0];
+	unsigned long rcount = 0;
+	unsigned long i1, i2;
+	
+	for(i1=1; i1<=pcount; i1++)
+		for(i2=i1; i2<=pcount; i2++)
+		{
+			unsigned long result = p[i1] * p[i2];
+			if(result >= limit)
+				break;
+			rcount++;
+		}
+
+	printf("%li\n", rcount);
+
+	free(p);
+	return 0;
+}
+