Thread: Menu Help

Ive got this menu I created...

Code:

int MainMenu(int c)
{ 
 printf("\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s",
 "-MAIN MENU-",
 "1. Initialize the list by reading in strings from the input and adding one by one to the linked list.",
 "2. Print all the strings in the list.",
 "3. Remove a string from a list (interactively).",
 "4. Add a string to the list (interactively).",
 "5. Search for a string in the list.",
 "6. Make a deep copy of the list.",
 "7. Concatenate two lists.",
 "8. Destory the list. A new list can be created by selecting 1.",
 "9. Quit.\n");
 
 scanf("%d", &c);
 
 return c;
}


 int main()
{
 struct Node * st = NULL;
 String string;
 int choice; 
 char yon;
 
 MainMenu(choice);
 
 if (choice == 1)
 {
	  yon = 'y';

	  if (yon == 'y')
	  {
	  printf("\n%s", "Please enter a string: ");
      scanf("%s", &string);
      AddNode(&st, string);
	  printf("\n%s", "Would you like to enter another, y or n?");
	  scanf("%c", &yon);
	  } 
	  else 
	  {
		 MainMenu(choice);
	  }
  }
  
 else if (choice == 2) 
 {
	 printf("\n%s", "Your list contains:\n");
     PrintList(st);
	 MainMenu(choice);
 }
 
 else if (choice == 3) {printf("\n%s", "You picked 3."); }
 
 else if (choice == 4) 
 {
	 printf("\n%s", "Please enter a string: ");
     scanf("%s", &string);
     AddNode(&st, string);
	 MainMenu(choice);
 }
 
 else if (choice == 5) {printf("\n%s", "You picked 5."); }
 
 else if (choice == 6) {printf("\n%s", "You picked 6."); }
 
 else if (choice == 7) {printf("\n%s", "You picked 7."); }
 
 else if (choice == 8) 
 {
	 DestroyList(&st);
	 printf("\n%s", "Your list has been destroyed. To create another, simply chose choice 1."); 
	 MainMenu(choice);
 }
 
 else 
 {
 printf("\n%s", "Bye Bye!");
 return 0;
 }
}

Now I am having three problems...

1. When it executes, it runs the menu, but no matter what choice I choose, it always exits. I think the initiation of the variable "choice" is the problem because if I declare it in the main as one of the choices, say "int choice = 1;" then it will run and no matter what choice I chose, it runs choice 1. I dont think it is getting the choice back from the MainMenu class. Please advise.

2. In choice 1, right after the user enters the string, it asks the user if they want to enter another one. But insted of letting them type a choice, the program exits. Not sure whats up with that. Please advise.

3. I dont know how, but after a given choice is complete, I need the program to go back to the main menu. I think that the way I have it set up works, but I am not sure, for I havent been able to get that far enough through the execution to see. Please advise.

A couple o' things that always catch ppl out here is memory allocation for your c-string, and also making sure it's null terminated. Post the whole thing and I'll give it a thorough look and tell you what's wrong where.

>scanf("%s", &string);
You do this a lot. It suggests that you don't quite understand your code. string is an instance of the String struct, not a char *. You want

Code:

scanf("%s", string.str);

Of course, you still haven't allocated memory to string.str, which is a pointer.

>node->str = string;
You're copying by value, but the pointer still points to the original memory from string in main. Your list will not print as you expect it to. You need to make a deep copy of the pointers so that they aren't lost when a new string is entered.

>struct Node * node = (struct Node *)malloc(sizeof(struct Node));
Don't cast malloc, it's hiding the fact that you forgot to include stdlib.h.

The following works for options 1 and 2. I didn't test the others:

Code:

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

typedef struct
{
  char *str;
  int len;
} String;

struct Node 
{
  struct Node * next;
  String str;
};


struct Node * AllocNode(String string)
{
  struct Node * node = (struct Node *)malloc(sizeof(struct Node));

  if(node != NULL)
  { 
    node->next = 0;
    node->str.len = strlen ( string.str );
    node->str.str = malloc ( node->str.len + 1 );
    if ( node->str.str != NULL )
      strcpy ( node->str.str, string.str );
  }

  return node;    
}


void DestroyList(struct Node ** st)
{
  struct Node * next, * prev = *st;

  while(prev != NULL)
  {
    next = prev->next;
    free(prev);
    prev = next;
  } 

  *st = 0;   
}


struct Node * AddNode(struct Node ** st, String string)
{
  struct Node * next = *st;
  struct Node * node = AllocNode(string);

  if(*st != NULL)
  {
    while(next->next != NULL)
    {
      next = next->next;
    }

    next->next = node;     
  } 
  else
  {
    *st = node;
  }  

  return node;
}


void PrintList(struct Node * st)
{
  struct Node * next = st;

  while(next != NULL)
  {
    printf("%s\n", next->str.str);

    next = next->next;
  } 
}

int MainMenu(void)
{ 
  int c = 0;
  printf("\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s",
    "-MAIN MENU-",
    "1. Initialize the list by reading in strings from the input and adding one by one to the linked list.",
    "2. Print all the strings in the list.",
    "3. Remove a string from a list (interactively).",
    "4. Add a string to the list (interactively).",
    "5. Search for a string in the list.",
    "6. Make a deep copy of the list.",
    "7. Concatenate two lists.",
    "8. Destory the list. A new list can be created by selecting 1.",
    "9. Quit.\n");

  scanf("%d", &c);

  return c;
}

int main()
{
  struct Node * st = NULL;
  String string;
  int choice = 0;
  char yon = 'y';
  char buff[BUFSIZ];

  string.str = buff;
  choice = MainMenu();

  do
  {
    if (choice == 1)
    {
      do
      {
        printf("%s", "Please enter a string: \n");
        scanf("%s", string.str);
        AddNode(&st, string);
        printf("%s", "Would you like to enter another string? y or n?\n");
        scanf(" %c", &yon);
      } 
      while (yon != 'n');
      choice = MainMenu();
    }

    else if (choice == 2) 
    {
      printf("%s", "Your list contains:\n");
      PrintList(st);
      choice = MainMenu();
    }

    else if (choice == 3) {printf("\n%s", "You picked 3.\n"); }

    else if (choice == 4) 
    {
      printf("%s", "Please enter a string: \n");
      scanf("%s", string.str);
      AddNode(&st, string);
      choice = MainMenu();
    }

    else if (choice == 5) {printf("\n%s", "You picked 5.\n"); }

    else if (choice == 6) {printf("\n%s", "You picked 6.\n"); }

    else if (choice == 7) {printf("\n%s", "You picked 7.\n"); }

    else if (choice == 8) 
    {
      DestroyList(&st);
      printf("%s", "Your list has been destroyed. To create another, simply chose choice 1.\n"); 
      choice = MainMenu();
    }
  }
  while (choice != 9);
  return 0;
}