Thread: delete function in singly linked list

Code:

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


struct node
{
    int data;
    struct node *next;
};
typedef struct node NODE;


NODE *create()
{ 
    return NULL;
}
    
int insert(int val, NODE *List);
void displayList();
int Length(NODE *head);
int deleteNode(NODE *List, int x);


int main()
{
    NODE *L = create();
    int val, p, choice, dp;
    char again;
    while(choice!=4)
    {
    clrscr();
    displayList(L);
    printf("\nMENU\n[1] Insert\n[2] View\n[3] Delete\n[4] Exit\n");
    printf("\nChoice? ");
    scanf("%d", &choice);
    switch(choice)
    {
        case 1:
        
            printf("\nValue to insert? ");
            scanf("%d", &val);
            L = insert(val, L);
            getch();
            break;
        
        case 2:
            displayList(L);
            getch();
            break;
        
        case 3:
            printf("\nValue to delete: ");
            scanf("%d", &dp);
            L = deleteNode(L, dp);
            getch();
            break;
            
        case 4:
            return 0;
            
        default:
            printf("\nINVALID INPUT!\n");
            break;
    }
    }
}






/***************************************************************/
void displayList(NODE *List)
{    
    if(List==NULL)
    {
        printf("There are no elements in the list!!");
    }
    else
    {
        while(List!=NULL)
        {
            printf ("%d -> ", List->data);
            List=List->next;
        }
    }


}






/***************************************************************/
int insert(int val, NODE *List)
{
    NODE *new;
    new = (NODE*)malloc(sizeof(NODE));
    if (new)
    {
        new -> data = val;
        new ->next = NULL;
        if(List==NULL)
        {
            List=new;
        }
        else
        {
            new -> next = List;
            List = new;
        }
    }
    printf("\nInsert successful!\n");
    return List;
    
}
  
  
/***************************************************************/
int Length(NODE *head)
{
    NODE *current = head;
    int count = 0;
    while (current != NULL)
    {
        count ++;
        current = current -> next;
        
    }
    
    return count;
}


int deleteNode(NODE *List, int x)
{
    NODE *tmp;
    tmp = List;
    if(tmp==NULL)
        printf("List is empty!");
    else
    {
        while(tmp->data!=x)
        {
            tmp = tmp ->next;
        }
        free(tmp);
        tmp = tmp ->next;
    }
    return tmp;
}

The above code is a SLL.
I have a problem in my deleteNode function.
I can't delete the exact data on the list.

Can anybody help me how to do this right?

Thanks

You need to find the node before the one that has the x. You will take that node and set it's next pointer to the x node's next pointer. then you can free() the x node and return.