Doubly Linked List

18_doublylinkedlist_v0.c

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


/* This program uses pointer, malloc and structs :) */

int main(int argc, char *argv[]) {
	
	/* Declaration of the structure to hold anniversaries data */
	typedef struct Track	{
		int track;
		char artist[50];
		char music[50];
		int duration;
		struct Track *next;                        /* Pointer to the next structure */
		struct Track *previous;                    /* Pointer to the previous structure */ 
		
	}Track_t;
	
	Track_t *first = NULL;					        /* Pointer to the first Register */
	Track_t *current = NULL;				        /* Pointer to the current Register */
	Track_t *last = NULL;					        /* Pointer to the previus Register */
	
	
	/* Test value for ending input */
	char test = '\0';
	 
	/* Variable to deal with buffer's cleaning */
	int c; 
	
	printf("\n\n_____________________!!!!!WELCOME TO JR'PLAYLIST!!!!'_______________________\n\n");

	for( ; ; )  /* Infinite loop; you do not have to worry about arrays and mess around with indexes */
	{
	    	printf("\nDo you What to enter a Track now (Y or N)?");
		scanf(" %c", &test);
		//while ((c = getchar()) != '\n' && c != EOF) { } 	/* clears input buffer */
	
		if(tolower(test) == 'n') break;
		
		/* Allocate memory to hold the structure */
		/* This statement allocates the space for each structure dynamically as it's requered */
		/* The malloc() function allocates the number of bytes specified by its argument and 
		   returns the address of the block of memory allocated as a pointer to type votrack */
		//ptr2Calendar[rcounter] = (Track_t*) malloc(sizeof(Track_t));
		current = (Track_t*) malloc(sizeof(Track_t));         				
		
		if(first == NULL)
		{
			first = current;                                /* Set pointer to first register */
			current->previous = NULL;                       /* The first node points previous to NULL */
		}
		else
		{
			last->next = current;  		                    /* Set next pointer for previous register */
			current->previous = last;                       /* Previous address for current node */
		}
			
		printf("\nPlease enter the Track Number: ");
		//scanf("%i", &Calendar[rcount].month);             /* Read the track of the person in the register */	
		//scanf("%i", &ptr2Calendar[rcounter]->month);
		scanf("%i", &current->track);		
		while ((c = getchar()) != '\n' && c != EOF) { } 	/* clears input buffer */	
			
		printf("\nPlease enter the Artist Name: ");
		gets(current->artist);
		//scanf("%s", &current->artist);
		//while ((c = getchar()) != '\n' && c != EOF) { } 
			
		printf("\nPlease enter the Music Name: ");
		gets(current->music);
		//scanf("%i", &current->music);		
		//while ((c = getchar()) != '\n' && c != EOF) { } 	/* clears input buffer */
			
		printf("\nPlease enter the Track Duration (sec): ");
		//scanf("%i", &Calendar[rcount].month);             /* Read the track of the person in the register */	
		//scanf("%i", &ptr2Calendar[rcounter]->month);
		scanf("%i", &current->duration);		
		while ((c = getchar()) != '\n' && c != EOF) { } 	/* clears input buffer */
 		
		current->next = NULL;  					            /* In case it is the last... */
		last = current;     	     				        /* Save address of the last register */
	}
	
	//current = first;                				        /* Starting at the beginning */
	
	/* Printing the receipt if everything is ok */
	printf ("\n You have Entered these Musics:\n\n"); 
	printf("__________________________Tracks______List____________________________\n");
	printf("| Track |  Artist Name  |         Music Title         | Time(sec) |\n") ;
	printf("----------------------------------------------------------------------\n");		
	/* This for loop prints the output and frees the memory allocated, block by block */	
	//for(int i = 0; i < rcounter; i++)
	while(current != NULL)     					            /* As long as we have a valtrack pointer */ 
	{		
		printf("| %i | %s | %s | %i |\n", current->track, current->artist, current->music, current->duration);
		
		last = current;    					                /* Save the pointer so we can free memory */
		//current = current->next;  				        /* Get the pointer to the next */
		current = current->previous;  				        /* PRINTTING IN REVERSE ORDER */
		
		/* It is very important to free each block of memory previously allocated;
		   If you don't keep track and don't free it after malloc, you might have memory leaks :/
		   it's considered good style to free memory as soon as you don't need it any more. Read this post:
		   https://stackoverflow.com/questions/654754/what-really-happens-when-you-dont-free-after-malloc */		   
		//free(ptr2Calendar[i]);     
		//free(previous); 
		free(last);
	}
	    printf("\n______________________________________________________________________\n");
            printf("\n______________________________________________________________________\n");
	
	return 0;
}
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