Recursive Sum Function

sum.c

//n is the last index of the array
int arr_sum(int arr[], int n )
{
  //base case
  if (n == 0)
  {
    return arr[0];
  }
  
  return (arr[n] + arr_sum(arr,n-1));
}

int main(void)
{
  int arr[] = {1,2,3,4,5};
  int sum;

  sum = arr_sum(arr,4);
  printf("\nsum is:%d\n",sum);

  return 0;
}

Grokking Algorithms exercise 4.1 in C.