Renamed llst to LL

Author: sunitgopal

LL.c

@@ -0,0 +1,280 @@
+#include <stdio.h> 
+#include "LL.h"
+
+/* For visualization: 4 --> 10 --> 7 --> 5 --> 16 */
+
+/* Globally declaring two static NODE pointers, head and tail */
+static NODE* head = NULL; 
+static NODE* tail = NULL;
+// Global/static pointers would anyway get initialized to NULL if left uninitialized
+
+
+int main(){
+
+ int hdata;
+ printf ("Enter desired head-node data\n");
+ scanf("%d", &hdata);
+
+ create (hdata);
+
+ append(9);
+ create (99);
+ 
+ insert(8, 0);
+ 
+ prepend(7);
+
+ insert (11, 3);
+ 
+ takeout(0);
+ append(7);
+
+ reverse();
+
+ sortAscndg();
+
+ return 0;
+}
+
+
+void create (int head_data){
+
+ if (head != NULL){
+ printf ("List already exists. Consider using append(%d) or insert(%d) instead\n", head_data, head_data);
+ return;
+ }
+ head = (NODE*) malloc (sizeof(NODE));
+ head->data = head_data;
+ head->ptr = NULL;
+ tail = head;
+ 
+ printf("LL after create(%d): \n", head_data);
+ print(head);
+ return;
+}
+
+
+void print (NODE* head){
+
+ NODE* iter = head;
+
+ if (NULL == iter){
+ printf ("Empty list. Nothing to print.\n");
+ return;
+ }
+ while (iter->ptr != NULL){ // exits once iter points at Tail node
+
+ printf ("%d --> ", iter->data);
+ iter = iter->ptr;
+ }
+ printf ("%d \n", iter->data); // BEAUTIFICATION: to avoid printing an arrow after Tail node
+ return;
+} 
+
+
+void append (int node_data){
+
+ /* ITCO presence of Tail pointer */
+/*
+ if (head == NULL){
+ printf("Empty list. Call create() first\n");
+ return;
+ }
+ NODE* temp = (NODE*) malloc (sizeof(NODE));
+ temp->data = node_data;
+ temp->ptr = NULL;
+ tail->ptr = temp;
+ tail = temp;
+ temp = NULL; // to avoid misuse of temp pointer
+ return;
+*/
+ 
+ /* ITCO absence of Tail pointer */
+
+ if (head == NULL){
+ printf("Empty list. Call create() first\n");
+ return;
+ }
+ NODE* temp = (NODE*) malloc (sizeof(NODE));
+ temp->data = node_data;
+ temp->ptr = NULL;
+ 
+ // Define iter NODE ptr to get to the end of LL
+ NODE* iter = head;
+ while (iter->ptr != NULL){ // exits when iter points to Tail node
+
+ iter = iter->ptr;
+ }
+ iter->ptr = temp;
+
+ printf("LL after append(%d): \n", node_data);
+ print(head);
+ return;
+}
+
+
+void insert (int node_data, int pos){
+
+
+ if (0 == pos){ // to cover the case of pos == 0
+
+ printf("Consider using prepend(%d) instead, but sure\n", node_data);
+ prepend(node_data);
+
+ return;
+ }
+ 
+ // else if // MODIFYLATER to cover pos > Tail node pos
+
+ NODE* newnode = (NODE*) malloc (sizeof(NODE));
+ newnode->data = node_data;
+ newnode->ptr = NULL; // to avoid indeterminacy
+ 
+ NODE* temp = head;
+ int count = 0;
+
+ while((temp->ptr != NULL) && (count != (pos-1))){ // Traverse till (pos-1) 
+ temp = temp->ptr;
+ count++;
+ }
+
+ if (count == (pos-1)){ // If reached the right index/pos 
+ newnode->ptr = temp->ptr;
+ temp->ptr = newnode;
+
+ printf("LL after insert(%d, %d): \n", node_data, pos);
+ print(head);
+
+ return;
+ }
+
+ else if (temp->ptr == NULL){ // If reached the end of the LL 
+ printf("No such index, thus appending \n");
+ append (node_data);
+
+ printf("LL after insert(%d, %d): \n", node_data, pos);
+ print(head);
+
+ return;
+ }
+
+ 
+}
+
+
+void prepend (int hnode_data){
+
+ NODE* newnode = (NODE*) malloc (sizeof(NODE));
+ newnode->data = hnode_data;
+ newnode->ptr = head; 
+ head = newnode;
+
+ printf("LL after prepend(%d): \n", hnode_data);
+ print(head);
+ return;
+}
+
+void takeout (int pos){
+
+ // if pos == 0 --> handle separately
+ // iter till pos-1
+ // iter->ptr = iter->ptr->ptr
+ // print taken out NODE data
+ // deallocate takenout NODE
+ // MODIFYLATER to cover pos == Tail NODE, as well as > Tail NODE
+
+ if (0 == pos){
+
+ NODE* temp = head; 
+ head = head->ptr;
+ printf ("Takenout NODE data = %d\n", temp->data);
+ free(temp);
+
+ printf("LL after takeout(%d): \n", pos);
+ print(head);
+ return;
+ }
+ NODE* iter = head;
+ int count = 0;
+ 
+ NODE* temp = NULL;
+ while (count != (pos-1)){ // exits when iter is at pos-1
+ 
+ iter = iter->ptr;
+ count++;
+ }
+ temp = iter->ptr;
+ iter->ptr = temp->ptr;
+ printf ("Takenout NODE data = %d\n", temp->data);
+ free(temp);
+
+ printf("LL after takeout(%d): \n", pos);
+ print(head);
+ return;
+}
+
+
+void reverse (void){
+
+ NODE* iter = head;
+
+ if (NULL == iter){
+
+ printf("Empty list. Nothng to reverse\n");
+ return;
+ }
+
+ NODE* iterp = NULL;
+ NODE* iterf = iter->ptr;
+
+ while (iter->ptr != NULL){
+
+ iter->ptr = iterp;
+ iterp = iter;
+ iter = iterf;
+ iterf = iterf->ptr;
+ }
+
+ iter->ptr = iterp;
+ head = iter;
+
+ printf("LL after reverse(): \n");
+ print(head);
+
+ return;
+}
+
+void sortAscndg (void){
+
+ // Using Selection Sort
+
+ NODE* iter = head;
+ if (NULL == iter){
+
+ printf("Empty list. Nothng to sort\n");
+ return;
+ }
+ NODE* iter2 = NULL;
+
+ while (iter->ptr != NULL){ 
+
+ iter2 = iter->ptr;
+ 
+ while (iter2 != NULL){
+
+ if (iter2->data < iter->data)
+ {
+ int tmp = iter->data;
+ iter->data = iter2->data;
+ iter2->data = tmp;
+ }
+ iter2 = iter2->ptr;
+ }
+ iter = iter->ptr; 
+ }
+
+ printf("LL after sortAscndg(): \n");
+ print(head);
+
+ return;
+}

LL.h

@@ -0,0 +1,25 @@
+#ifndef LL_H
+#define LL_H
+
+#include <stdlib.h> //malloc
+
+/* Declaring global struct of type Node, and alias NODE */
+typedef struct Node
+{
+ int data;
+ struct Node* ptr;
+} NODE;
+
+
+/* Function Declarations */
+
+void create (int head_data); 
+void print (NODE*); 
+void append (int node_data);
+void insert (int node_data, int pos); // pos takes index values, not count values
+void prepend (int head_data);
+void takeout (int pos); // couldn't use the name "remove" BCZ it is already used in stdio.h
+void reverse (void); // MODIFYLATER to take head pointer to cover the case of multiple lists
+void sortAscndg (void);
+
+#endif // LL_H