linked_lists_4.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct sPerson {
	int age;
	struct sPerson *nextInLine;
};

void printPerson(const struct sPerson *person, const char *comment)
{
    if (person == NULL)
    {
        printf("%s is NULL\n", comment);
    }
    else
    {
       printf("%s: age:%d address:%p nextInLine:%p\n", 
            comment,
            person->age, 
            person,
            person->nextInLine);
    }
}

void PrintList(const struct sPerson *list)
{
	printf("Printing List:\n");
	const struct sPerson *t;
	t = list;
    if(t == NULL)
    {
        printf("list is empty\n");
    }
    else
    {
        while(t)
        {
            printPerson(t, "t");
            t = t->nextInLine;
        }
    }
}

struct sPerson *getNewPerson(const int age) 
{
    struct sPerson *newPerson = NULL;
    newPerson = malloc(sizeof(struct sPerson));
	if(newPerson != NULL)
	{
		newPerson->nextInLine = NULL;
		newPerson->age = age;
		printf("new person at %p\n", newPerson);
	}
	else
	{
		printf("Allocation Failure!! \n");
	}
    return newPerson;
}

void CleanUp(struct sPerson *list)
{
    struct sPerson *next;
    while(list)
    {
        next = list->nextInLine;
        printf("Cleaning %d\n", list->age);
        free(list);
        list = next;
    }
}

int main() 
{
	printf("** START **\n");

    struct sPerson *first = NULL;
    struct sPerson *added = NULL;
	struct sPerson *pStart = NULL;

    char command[64];
    char start;
	int age;

    while(1)
    {
        printf( "Enter a command or value : ");
		fgets(command, 64, stdin);
		if (strcmp("q\n", command) == 0) 
		{
			printf("Quitting..\n");
			break;
		}
		else if (strcmp("print\n", command) == 0) 
		{
			printf("Printing..\n");
			PrintList(first);
		}
        else
        {
            if (sscanf(command, "%c %d", &start, &age) != 0)
            {
				printf("Adding %d at %c\n", age, start);
                if (first == NULL)
                {
                    first = getNewPerson(age);
					if(first != NULL)
					{
						added = first;
					}
                }
                else if(start == 's')
                {
                    pStart = getNewPerson(age);
                    if (pStart != NULL)
                    {
                        pStart->nextInLine = first;
                        first = pStart;
                        pStart = NULL;
                    }
                }
                else
                {
                    added->nextInLine = getNewPerson(age);
					if(added->nextInLine != NULL)
					{
						added = added->nextInLine;
					}
                }
                
            }
        }
        
    }

    CleanUp(first);
    first = NULL;
    added = NULL;
    pStart = NULL;

	return 0;
}