Array of singly linked list won't delete node - c

Question

I have an array[4] where each index of the array has a singly linked list that holds the following information: name, size. The switch statement controls what index the information will go into according to the size of the party.
Problem: When trying to delete a node according to the size (user inputs) the node will not delete.
I know that all of the cases of deletion have the proper syntax but I cannot figure out why my node will not delete. Appreciate any help.
Code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef struct node
{
char name[20];
int size;
struct node *next;
}node;
node* head[4]={NULL,NULL,NULL,NULL};
node* tail[4]={NULL,NULL,NULL,NULL};
//
// proto's
//
void add_party(int, char name[], int size);
void delete_party(char name[], int size);
void list_parties(void);
void change_p_size(char name[], int size);
//
// main function
//
int main()
{
int x;
while (1)
{
fflush(stdin);
printf("\n\nEnter 1 to add a party\nEnter 2 to remove a party\nEnter 3 for the list of the party\nEnter 4 to change party size.\nEnter 5 to quit.\n\n");
// user interface
scanf("%d",&x);
switch(x)
{
char name[20]; //local variables
int size;
case 1:
printf("\nParty Name: ");
scanf("%s", name);
printf("\nParty Size: ");
scanf("%d", &size);
if(size == 0)
{
printf("\nThat is not a valid command. Party not added!\n");
}
if(size >= 1 && size <= 2)
{
add_party(0, name, size);
}
else if(size >= 3 && size <= 4)
{
add_party(1, name, size);
}
else if(size >= 5 && size <= 6)
{
add_party(2, name, size);
}
else if(size >= 7)
{
add_party(3, name, size);
}
break;
case 2:
printf("\nSize of party to delete: ");
scanf("%i", &size);
delete_party(NULL, size);
break;
case 3:
list_parties();
break;
case 4:
change_partysize();
break;
case 5:
exit(0);
default:
continue;
}
}
}
//
//add function
//
void add_party(int h, char *name, int size)
{
//create a new node
int i=0;
int breaker = 0;
node *p;
node *new_item;
new_item = (node *)malloc(sizeof(node)); // allocate memory the size of the struct
strcpy(new_item->name,name);
new_item->size = size;
if(head[h] == NULL && tail[h] == NULL) // if an empty list, create a head and tail
{
head[h] = new_item;
tail[h] = head[h];
new_item->next = NULL;
return;
}
//traversal
for(i=0; i<4; i++)
{
p = head[i];
while(p != NULL)
{
//check that no repeating names. delete nodes that do have repeating names
if(strcmp(p->name,name) == 0)
{
printf("\nSorry, that name is already taken\n");
free(new_item);
return;
}
p = p->next; //go to the next node in the list
}
}
tail[h]->next = new_item;
new_item->next = NULL;
tail[h] = new_item;
}
//
//delete function
//
void delete_party(char *name, int size)
{
int i=0;
int breaker = 0;
node *p;
node *previous;
if(name != NULL)
{
for(i=0; i<4; i++)
{
p = previous = head[i]; //make sure previous trails behind head
while(p != NULL)
{
int c = (strcmp(p->name,name)==0);
if(c==0)
{
breaker = 1;
break;
}
else
previous = p;
p = p -> next;
}
if(breaker==1)
break;
}
}
else
{
int group = -1;
if(size == 1 || size == 2)
{
group = 0;
}
if(size == 3 || size == 4)
{
group = 1;
}
if(size == 5 || size == 6)
{
group = 2;
}
if(size >= 7)
{
group = 3;
}
for(i = group; i > -1; i--)
{
node *p = head[i];
node *previous = head[i];
while(p != NULL)
{
if(p <= size)
{
breaker = 1;
break;
}
else
{
previous = p;
p = p-> next;
}
}
if(breaker)
break;
}
}
if(p == NULL)
return;
if(head[i] == tail[i] && head[i] != NULL) // case 1, empty list
{
printf("\nList is empty!\n");
return;
}
else if(p == tail[i] && p == head[i]) // case 2, one element
{
head[i] = NULL;
tail[i] = NULL;
free(p);
}
else if(p == head[i]) // case 3, delete from the head
{
head[i] = head[i] -> next;
tail[i] = NULL;
free(p);
}
else if(p == tail[i]) // case 4, delete from tail
{
tail[i] = previous;
tail[i] -> next = NULL;
free(p);
}
else // case 5, delete from middle
{
previous -> next = p -> next;
free(p);
}
}
//
// list function
//
void list_parties(void)
{
int i = 0;
node *p=head;
for(i=0; i<4; i++)
{
p=head[i];
while(p != NULL)
{
printf("\n\n%s, %d\n\n", p->name, p->size);
p=p->next;
}
}
}
//
// change function
//
void change_partysize(char *name, int size)
{
int absolute_value = 0;
int comparison = 0;
int current_size = 0;
printf("\nWhat name is your party under?\n");
scanf("%s", name);
//check if the name
printf("\nWhat would you like to change the size to?\n");
scanf("%d", &size);
node *p;
while(p != NULL)
{
if(p->name == name) //new size falls into same range as the size coorelating to the name
{
current_size = p->size;
absolute_value = abs(size - current_size);
comparison = size - current_size;
if(current_size > 7 && size > 7)
{
current_size = size;
return;
}
else if(absolute_value >= 1)
{
//delete the node's value but not the name
delete_party(NULL, size);
//insert node with new name & dif size
add_party(NULL, name, size);
}
else
{
printf("\nYou did not enter a different party size\n");
return;
}
}
}
}

Answer 1

You're declaring new variables p and previous inside the for loop when you delete by size. So when the code after the loop uses these variables, it's using the uninitialized variables declared at the top of the function. Get rid of the declarations and just assign the variables.
Also, if (p <= size) appears to be a typo for if (p->size <= size). I'm surprised you didn't get a compiler warning for that.
You can also replace the if(breaker) check with a test in the for header.
for(i = group; !breaker && i > -1; i--)
{
p = head[i];
previous = head[i];
while(p != NULL)
{
if(p->size <= size)
{
breaker = 1;
break;
}
else
{
previous = p;
p = p-> next;
}
}
}