#include <stdio.h>

int sum1D(int n, int a[]);
int sum2D(int rows, int cols, int a[rows][cols]); // see "variable length arrays"
void double1D(int n, int a[]);

int main() {
  int a[5] = {2, 3, 5, 7, 11};
  int a2[3][3] = {{1, 1, 1}, {1, 2, 3}, {2, 3, 4}};
  double1D(5, a);
  printf("%d\n", sum1D(5, a));
  printf("%d\n", sum2D(3, 3, a2));
  printf("%d\n", sum1D(3, a2[1])); // a2[1] is row 1 of a2; rows are 1D arrays!
  printf("%d\n", sum1D(5, a2[1])); // lying about size of row -- what happens?
}

int sum1D(int n, int a[])
{
  int sum = 0;
  for (int i = 0; i < n; i++)
    {
      sum += a[i];
    }
  return sum;
}

int sum2D(int rows, int cols, int a[rows][cols])
{
  int sum = 0;
  for (int r = 0; r < rows; r++)
    {
    for (int c = 0; c < cols; c++)
      {
	sum += a[r][c];
      }
    }
  return sum;
}

void double1D(int n, int a[])
{
  for (int i = 0; i < n; i++)
    {
      a[i] *= 2;
    }
}