/* ========================================================================== */
/*                                                                            */
/*   structures.c                                                             */
/*   (c) 2017 K. J. Rock                                                      */
/*                                                                            */
/*   This shows how to create and use a structure with pointers               */
/*   linked into a list                                                       */
/* ========================================================================== */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

struct db
	{
	int id;
	int age;
	float salary;
	struct db *next;
	};

struct db *head, *ep, *node, *temp;

int main()
	{
	srand((unsigned) time(NULL)); // randomize by seeding from time

   temp = (struct db *) malloc (sizeof(struct db));
	temp->next = NULL;	// define end of list with guard value NULL
	
	temp->id = 42;       // instantiate the founder's info
	temp->age = rand() % 40 + 20;
	temp->salary = 35080.15 + (rand() % 1250);
	
	head = temp;  			// store beginning of list as head pointer

   // allocate space & instantiate the rest of the crew
	for (int i=1; i<27; i++)
		{
      node = (struct db *) malloc (sizeof(struct db));
		temp->next = node;// add new node to end of growing list
		node->next = NULL;// set end of list with our standard guard value
		temp = node;		// keep track of this node so you can add to it
      temp->id = i;		// fill data fields of new node
		temp->age = rand() % 40 + 20;   // no employees under 20
		temp->salary = (float) ((rand() % 40000) + 60000);  // min salary 60000
		}

	ep = head;  			// set employee pointer to start of list
	while (ep != NULL)
		{
      printf("Employee #%2d is %2d years old earning $%6.2f \n", ep->id, ep->age, ep->salary);
		ep = ep->next;  	// step to next employee
		}

	float sum = 0;
	int count = 0;
	int age = 0;

	ep = head;
	while (ep != NULL)
		{
		age += ep->age;
		sum += ep->salary;
      count++;
		ep = ep->next;
		}

	printf("\nPayroll $%8.2f \n", sum);
   printf("average paycheck $%8.2f \n", sum / count );
	printf("Average age %2d \n", age / count );  // integer divide so rough estimate
	//printf("%2d \n", count);
	}