brute force method to find primes and add them

project_euler/Problem 10/sol1.c

@@ -0,0 +1,37 @@
+#include <stdio.h>
+#include <math.h>
+#include <stdlib.h>
+
+char is_prime(long n)
+{
+    for (long i = 2; i < sqrtl(n) + 1; i++)
+        if ( n % i == 0)
+            return 0;
+
+    return 1;
+}
+
+
+long long sum_of_primes(long N)
+{
+    long long  sum = 2;
+
+    for (long i = 3; i < N; i+=2)   /* skip even numbers */
+        if (is_prime(i))
+            sum += i;
+
+    return sum;
+}
+
+
+int main(int argc, char* argv[])
+{
+    long n = 100;
+
+    if (argc == 2)  /* if command line argument is provided */
+        n = atol(argv[1]);  /* use that as the upper limit */
+
+    printf("%ld: %lld", n, sum_of_primes(n));
+
+    return 0;
+}