Summation Triangle sucessful submission in C

Codewars/C/SummationTriangle.c

@@ -0,0 +1,62 @@
+// Problem site: https://www.codewars.com/kata/63579823d25aad000ecfad9f/
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <math.h>
+
+long long pg_approach(unsigned);
+
+long calculate(int j, int i)
+{
+  return (2 * j + i + 1) * pow(-1, 2 * j + i);
+}
+long brute_force(int n)
+{
+  n++;
+  int start_point = 0;
+  int total_sum = 0;
+  for (int i = 0; i < n; i++)
+  {
+    for (int j = start_point; j < n; j++)
+    {
+      int triangle_elt = calculate(i, j);
+      total_sum += triangle_elt;
+    }
+    start_point++;
+  }
+  return total_sum;
+}
+long long get_sum(unsigned n)
+{
+  return pg_approach(n);
+}
+
+long long pg_approach(unsigned n)
+{
+  long long results[n];
+  memset(results, 0, n);
+  results[0] = 1;
+  results[1] = 5;
+  if (n == 0)
+    return 1;
+  if (n == 1)
+    return -5;
+  unsigned current_col = 1;
+  long long increase_factor = 4;
+  while (current_col < n)
+  {
+    current_col++;
+    if (!(current_col % 2))
+      increase_factor += 1;
+    else
+      increase_factor += 3;
+    results[current_col] = increase_factor + results[current_col - 1];
+  }
+  return (current_col % 2) ? (-1) * results[current_col] : results[current_col];
+}
+int main()
+{
+  for (int i = 0; i < 10; i++)
+    printf("\nteste %d:\n\tBrute force: %ld , PG: %lld", i, brute_force(i), pg_approach(i));
+  return 0;
+}