commit llst.c

Author: sunitgopal

llst.c

@@ -0,0 +1,200 @@
+#include <stdio.h>
+#include <stdlib.h> //malloc
+
+struct Node
+{
+ int data;
+ struct Node* link;
+};
+
+struct Node* createll ();
+void printll (struct Node* h);
+void reversell (struct Node* h);
+void deletep (struct Node* h, int P);
+void insertp (struct Node*, int, int);
+
+int main()
+{
+ struct Node* head = NULL; //declared and initialized pointer to head node 
+ 
+ //now, start inserting nodes to this ll 
+
+ 
+ int p = 3; //position to delete node
+ int newdata = 55;
+ struct Node* temp = NULL; //declared and initialized temp node pointer to add new nodes
+ 
+ head = createll();
+/* 
+ head = (struct Node*) malloc (sizeof(struct Node)); //allocated heap memory for head node
+ head->data = n;
+ head->link = NULL;
+
+ temp = (struct Node*) malloc (sizeof(struct Node)); //allocated heap memory for second node
+ temp->data = ++n;
+ temp->link = NULL;
+ head->link = temp;
+
+ temp = (struct Node*) malloc (sizeof(struct Node)); //allocated heap memory for third node
+ temp->data = ++n;
+ temp->link = NULL;
+ (head->link)->link = temp;
+
+ temp = (struct Node*) malloc (sizeof(struct Node)); //allocated heap memory for fourth node
+ temp->data = ++n;
+ temp->link = NULL;
+ ((head->link)->link)->link = temp;
+ 
+*/
+
+ printll (head);
+
+ //free(temp); //free function frees the heap location pointed to by its argument, essentially, no more of that piece of heap memory now available for use
+ //free(temp1);
+
+ /* created a 3 ele list so far*/
+ /* Now, reverse it and print it too*/
+
+ //reversell (head);
+
+ /* Now, delete pth node*/
+
+ deletep(head, p);
+ printll (head);
+
+ insertp (head, p, newdata);
+ printll (head);
+
+ return 0; 
+}
+
+struct Node* createll()
+{
+ struct Node* h = NULL;
+ struct Node* temp = NULL;
+ int n = 3; //for incrementing node data; first node starts with data = 3
+ 
+ h = (struct Node*) malloc (sizeof(struct Node));
+ h->data = n;
+ h->link = NULL;
+
+ temp = (struct Node*) malloc (sizeof(struct Node)); //allocated heap memory for second node
+ temp->data = ++n;
+ temp->link = NULL;
+ h->link = temp;
+
+ temp = (struct Node*) malloc (sizeof(struct Node)); //allocated heap memory for third node
+ temp->data = ++n;
+ temp->link = NULL;
+ (h->link)->link = temp;
+
+ temp = (struct Node*) malloc (sizeof(struct Node)); //allocated heap memory for fourth node
+ temp->data = ++n;
+ temp->link = NULL;
+ ((h->link)->link)->link = temp;
+
+ return h;
+}
+
+void printll (struct Node* h)
+{
+ struct Node* temp = NULL;
+ for (temp = h; temp!=NULL; temp = temp->link)
+ {
+ printf("%d ", temp->data);
+ }
+ printf ("\n");
+}
+
+void reversell (struct Node* h)
+{
+ struct Node* prev = NULL;
+ struct Node* curr = NULL;
+ struct Node* next = NULL;
+ curr = h;
+ while (curr->link != NULL)
+ {
+ next = curr->link;
+ curr->link = prev;
+ prev = curr;
+ curr = next;
+
+/* Debugging stmnts:
+ printf("prev points to %d\n", prev->data);
+ printf("curr points to %d\n", curr->data);
+ printf("next points to %d\n\n", next->data); */
+ }
+ curr->link = prev;
+ h = curr;
+ printll (h);
+}
+
+void deletep (struct Node* h, int P)
+{
+ /*first check if there is a Pth node*/
+ struct Node* temp = NULL;
+ struct Node* prev = NULL;
+ struct Node* next = NULL;
+ int i;
+ for (temp = h, i = 0; temp != NULL; temp = temp->link)
+ {
+ i++;
+ }
+ printf("i = %d\n", i);
+ if (i < P)
+ {
+ printf("there is no pth node\n");
+ }
+ else
+ {
+ for (temp = h, i = 0; i < P; i++, temp = temp->link)
+ {
+ if (i == (P-1))
+ {
+ prev = temp;
+ break;
+ }
+ }
+ temp = temp->link; //node to be deleted
+ next = temp->link;
+ prev->link = next;
+ free(temp);
+ }
+
+
+}
+
+void insertp (struct Node* h, int p, int nodedata)
+{
+ //check if there is a p-1th node at all
+
+ int count = 0;
+ struct Node* temp = NULL;
+ struct Node* newnode = NULL;
+
+ for (temp = h; temp != NULL; temp = temp->link)
+ {
+ count++;
+ }
+ printf("intermediateo/p count = %d\n", count);
+
+ if(count < (p-1)) //no p-1 th node at all
+ {
+ printf("ll has < p-1 nodes\n");
+ return;
+ }
+ else //yes p-1 th node
+ {
+ newnode = (struct Node*) malloc (sizeof(struct Node));
+ newnode->data = nodedata;
+ newnode->link = NULL;
+
+ int i;
+ for (i = 1, temp = h; i<p-1; temp = temp->link, i++)
+ {
+
+ }
+ newnode->link = temp->link;
+ temp->link = newnode;
+ }
+}