projecteuler solution 065

1 files changed, 40 insertions, 0 deletions

diff --git a/src/projecteuler/065.c b/src/projecteuler/065.c
new file mode 100644
index 0000000..3e93085
--- /dev/null
+++ b/src/projecteuler/065.c
@@ -0,0 +1,40 @@
+#include <gmp.h>
+#include <stdio.h>
+
+#define limit 100
+
+unsigned int start = 2;
+unsigned int factors[limit-1];
+
+int main(void)
+{
+	int pos, k=1, sum;
+	mpz_t numerator, denominator;
+
+	for(pos=0; pos<limit-1; pos++)
+	{
+		if(pos % 3 == 1)
+			factors[pos] = 2*(k++);
+		else
+			factors[pos] = 1;
+	}
+
+	mpz_init_set_ui(numerator, 1);
+	mpz_init_set_ui(denominator, factors[limit-2]);
+	for(pos=limit-3; pos>=0; pos--)
+	{
+		mpz_addmul_ui(numerator, denominator, factors[pos]); // numerator *= denominator * factors[pos]
+		mpz_swap(numerator, denominator);
+	}
+
+	mpz_addmul_ui(numerator, denominator, start); // numerator += denominator * start
+
+	sum = 0;
+	while(mpz_cmp_ui(numerator, 0) > 0)
+		sum += mpz_fdiv_q_ui(numerator, numerator, 10);
+
+	printf("%li\n", sum);
+
+	return 0;
+}
+