LinkBack URL
About LinkBacks
Hello, i am now learning the linked lists, i read about them, and saw some example codes, but most of them had functions which needed a pointer to head as an argument, then i decided to implement linked list myself.
Most of my functions require just pointer to list, and specific value to operate. If someone would like to take a look at my code, just say me what you think...and especially i want you to pay more attention to the removenode function... i implemented such operation using shifting of values... what do you think?
The linked list is just simple order of data in ascending format.. here is the full working code:
And also please pay attention on how i identify the empty list...that casting like (struct node *)-1.. waht do you think about this method?Code:#include <stdio.h> #include <stdlib.h> #define snapd(expr) printf(#expr " = %d\n", expr); #define snapd(expr) printf(#expr " = %d\n", expr); /* Function prototypes */ struct node *createlist(int value); void printlist(struct node *list); void find(struct node *list, int value); void removenode(struct node *list, int value); void insert(struct node *list, int value); /* Node definition */ struct node { int data; struct node *ptr; }; /* This function creates the linked list with the first element equal to its argument */ struct node *createlist(int value) { struct node *first; first = (struct node*)malloc(sizeof(struct node)); first->data = value; first->ptr = NULL; return first; } /* This function prints out the contents of the linked list */ void printlist(struct node *list) { if (list->ptr == (struct node *)-1) { printf("The list is empty!\n"); return; } while (list->ptr != NULL) { printf("%d\n", list->data); list = list->ptr; } if (list->ptr == NULL) { printf("%d\n", list->data); } } void find(struct node *list, int value) { struct node *previous = list; if (list->data == value) { printf("The element %d have been at the beginning of the list before %d\n", value, list->ptr->data); return; } while (list->ptr != NULL) { if (list->data == value && list->ptr != NULL) { printf("The element %d have been found between %d and %d\n", value, previous->data, list->ptr->data); return; } previous = list; list = list->ptr; } if (list->data == value) { printf("The element %d have been found at the end of the list after %d\n", value, previous->data); return; } printf("The element %d is not found in the list...\n"); } /* This function removes the node with specified value from the linked list */ void removenode(struct node *list, int value) { struct node *previous, *next, *first = list; int i; if (list->ptr == (struct node *)-1) { printf("The list is already empty!\n"); return; } //if the list contains only one element, free the list and exit function //then set a flag that this element is not a member of the linked list anymore if (list->data == value && list->ptr == NULL) { list->ptr = (struct node*)-1; //set the flag free(list); return; } for (i = 0; list->data != value; i++) { previous = list; list = list->ptr; } if (i != 0) { next = list->ptr; previous->ptr = next; free(list); } else { //shift all the elements to the left for (;;) { list->data = list->ptr->data; list = list->ptr; if (list->ptr == NULL) break; } //remove the last element list = first; while (list->ptr != NULL) { previous = list; list = list->ptr; } previous->ptr = NULL; free(list); } } /* This function inserts the value in the appropriate position in the linked list */ void insert(struct node *list, int value) { struct node *newnode; struct node *previous = list; //create an empty new node newnode = (struct node*)malloc(sizeof(struct node)); //scan until the end of the list while (list->ptr != NULL) { if (value > list->data) { previous = list; } //if it is less than current, and more than previous, insert value between them if ( (value < list->data) && (value > previous->data) ) { previous->ptr = newnode; newnode->ptr = list; newnode->data = value; printf("%d is inserted between %d and %d!\n", value, previous->data, list->data); break; } if (value == list->data) { printf("There is already value %d in the list!\n", value); break; } if (value < list->data) { printf("%d is added before %d...\n", value, list->data); newnode->data = list->data; newnode->ptr = list->ptr; list->data = value; list->ptr = newnode; break; } list = list->ptr; } if (list->ptr == NULL) { //if the value is more than the last element add the last element with new value if (value > list->data) { newnode->data = value; newnode->ptr = NULL; list->ptr = newnode; printf("%d is added after %d...\n", value, list->data); } if (value == list->data) { printf("There is already value %d in the list!\n", value); } if (value < list->data) { printf("%d is added before %d...\n", value, list->data); newnode->data = list->data; newnode->ptr = list->ptr; list->data = value; list->ptr = newnode; } } } void main (int argc, char *argv[]) { struct node *mylist; int value; int command; printf("Enter the first element of the linked list to be created: "); scanf("%d", &value); mylist = createlist(value); printf("Available commands:\n"); printf("1 - add new element:\n"); printf("2 - remove element:\n"); printf("3 - print the list:\n"); printf("4 - find a value in a list:\n"); printf("0 - quit program:\n"); printf("Enter command: "); for(;;) { scanf("%d", &command); switch (command) { case 1: printf("Enter the value to be added: "); scanf("%d", &value); //if the list is empty, create the new list again if (mylist->ptr == (struct node *)-1) { mylist = createlist(value); } else //otherwise, insert new value in the current list insert(mylist, value); printf("Enter the next command "); break; case 2: printf("Enter the value to be removed: "); scanf("%d", &value); removenode(mylist, value); printf("Enter the next command "); break; case 3: printf("Linked list values:\n"); printf("===================\n"); printlist(mylist); printf("===================\n"); printf("Enter the next command "); break; case 4: printf("Enter the value to be searched for: "); scanf("%d", &value); find(mylist, value); printf("Enter the next command "); break; case 0: return; break; default: printf("wrong command!\n"); printf("Available commands:\n"); printf("1 - add new element:\n"); printf("2 - remove element:\n"); printf("3 - print the list:\n"); printf("4 - find a value in a list:\n"); printf("0 - quit program:\n"); printf("Enter command: "); break; } } }
dont know why...strange...thats why i decided to implement it like i did 
Originally Posted by BlackOps 
