Menu problem involving structs

This is a discussion on Menu problem involving structs within the C Programming forums, part of the General Programming Boards category; I am currently doing a Queue program a using structs and linked lists. Most of it works fine however the ...

  1. #1
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    Menu problem involving structs

    I am currently doing a Queue program a using structs and linked lists. Most of it works fine however the menu used to drive it keeps having runtime errors when i try to print the queue.
    Am I doing something wrong?

    functions

    Code:
    CTaxi_addTaxi(int TaxiReg)
    {
    	struct node *temp,*r;
    	temp= (struct node *)malloc(sizeof(struct node));
    	temp->data=TaxiReg;
    	r=(struct node *)p;
    
    	if (p == NULL)
    	{
    		p=temp;
    		p->next =NULL;
    	}
    	else
    	{
    		while( r->next != NULL)
    		r=r->next;
    		r->next =temp;
    		r=temp;
    		r->next=NULL;
    	}
    }
    
    CTaxiDelete(char taxi)
    {
    	struct node *temp, *m;
    	temp=p;
    	while(temp!=NULL)
    	{
    		if(temp->data==taxi)
    		{
    			if(temp==p)
    			{
    				p=temp->next;
    				free(temp);
    				return;
    			}
    			else
    			{
    				m->next=temp->next;
    				free(temp);
    				return;
    			}
    		}
    		else
    		{
    			m=temp;
    			temp= temp->next;
    		}
    	}
    }
    
    CTaxi_printQueue(struct node *r)
    {
    	r=p;
    	if(r==NULL)
    	{
    		printf("Taxi Rank is currently empty!");
    		return;
    	}
    
    	while(r!=NULL)
    	{
    		printf(" -> %d ",r->data);
    		r=r->next;
    	}
    	printf("/n");
    }
    menu

    Code:
    main()
    {
    	int menuChoice = 0;
    	p=NULL;
    	while(menuChoice != 4)
    	{
    		printf("1.Add Taxi\n");
    		printf("2.Delete Taxi\n");
    		printf("3.Print current taxi queue\n");
    		printf("4.Exit\n");
    		printf("Enter a choice from the above menu:");
    		scanf("%d",&menuChoice);
    		
    		switch(menuChoice)
    		{
    			case 1:
    			{
    				int TaxiReg;
    				printf("Please enter a reg no :\n");
    				scanf("%d",&TaxiReg);
    				CTaxi_addTaxi(TaxiReg);
    				break;
    			}
    			
    			case 2:
    			{
    				int TaxiReg;
    				printf("Please enter a reg no to delete :\n");
    				scanf("%d",&TaxiReg);
    				CTaxiDelete(TaxiReg);
    				break;
    			}
    			
    			case 3:
    			{
    				struct node *n;
    				printf("The Current taxi queue is:\n");
    				CTaxi_printQueue(n);
    				break;
    			}
    			
    			case 4:
    			{
    				menuChoice =4;
    				return;
    			}
    		}
    	}
    }
    Also is there a way to search for a specific node in the list? So if I wanted to find a particular taxi entered by the user it will display it.

    Thanks for any help/suggestions given
    Last edited by NyHoK; 03-31-2009 at 08:47 AM.

  2. #2
    Kernel hacker
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    Perhaps we need to see the "addQueue" function?

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
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    My bad, edited the first post again

  4. #4
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    When dealing with a queue, it is much simpler to have two variables, one representing the "head" of the queue, and one for the "tail" (tail where things are entered, head is where things are taken off).

    I'm sure someone else will spot it, but I can't actually see anything wrong with teh code.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  5. #5
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    I have been staring at it for ages and can't figure it out. Any idea on how to implement searches on linked lists?

  6. #6
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    Quote Originally Posted by NyHoK View Post
    I have been staring at it for ages and can't figure it out. Any idea on how to implement searches on linked lists?

    Something like this:
    Code:
    node *p;
    for(p = head; p; p = p->next)
    {
       if (p->member == what_you_search_for)
         break;
    }
    if (p) ... we found something.
    There is no other way than to walk along the list and check each item.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

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