Upload files to "ex1C_summation_of_specified_numbers"

ex1C_summation_of_specified_numbers/special_sum.cpp

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+#include "special_sum.h"
+
+size_t gauss_sum(size_t n)
+{
+    return (n*(n+1))/2;
+}
+
+size_t special_sum_loop(size_t n)
+{
+    size_t sum = 0;
+    for (size_t i = 1; i < n+1; ++i)
+    {
+        if (i % 3 == 0 || i % 5 == 0)
+        {
+            sum += i;
+        }
+    }
+    return sum;
+}
+
+size_t special_sum_noloop(size_t n)
+{
+    size_t factor_3 = gauss_sum(n/3);   // dividing int by int automatically gets rounded off
+    size_t factor_5 = gauss_sum(n/5);
+    size_t factor_15 = gauss_sum(n/15);
+
+    return factor_3*3 + factor_5*5 - factor_15*15;
+}