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Circular_DLL.c
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Circular_DLL.c
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//To implement insertion and deletion operations in a circular doubly linked list using menu driven flow of control
//02.03.19
#include<stdio.h>
#include<process.h>
#include<stdlib.h>
#include<conio.h>
//Macro for easy use of malloc for memory allocation
#define Malloc(a) (a*)(malloc(sizeof(a)))
//Self referential structure for node creation in linked list
typedef struct nodeStructure{
int data;//data storage
struct nodeStructure *next;//points to next node in list
struct nodeStructure *previous;//points to previous node in list
};
//Declaration of first and last node pointers
struct nodeStructure *firstNode;
struct nodeStructure *lastNode;
//Function prototype and declaration for operations
//For inserting the nodes
void insertInList();
void putNodeAtStart();
void putNodeAtEnd();
void putNodeAtPosition();
//For deleting the nodes
void deleteFromList();
void removeNodeFromStart();
void removeNodeFromEnd();
void removeNodeAtPosition();
//Get values to store in the node
int getNodeValue();
//To display the nodes in the list
void getNodes();
//Searching for a user input data value in nodes of the linked list
struct nodeStructure* searchInNodes();
//main() opens
void main(){
int answer;
//For continuous display of switch-case menu
while(1){
system("cls"); //Clears the screen before each run of menu
printf("\nCircular Double Linked List Operations\n");
printf("01. Insertion in linked list\n");
printf("02. Deletion from linked list\n");
printf("03. Display the linked list\n");
printf("04. Exit\n");
scanf("%d", &answer);
//Switch-case for the user choice
switch (answer){
case 1: //For insertion in the linked list
insertInList();
break;
case 2: //For deletion from the linked list
deleteFromList();
break;
case 3: //For displaying the nodes in list
getNodes();
break;
default: //Default case for exiting the program
exit(0);
break;
}
}
getch();
}//main() closes
//Function definition for operations
struct nodeStructure* searchInNodes(){
struct nodeStructure *searchNode;
int valueFound = 0, searchValue;
//Get value to search from user
printf("Enter value to search \n");
scanf("%d", &searchValue);
//Declare new node for traversing the list
struct nodeStructure *scanNode;
scanNode = firstNode;
//Traverse the list till the lastNode is encountered (which points to the first node)
searchNode = NULL;
if (scanNode->data == searchValue){ //If value is found in the first node
valueFound = 1;
searchNode = firstNode;
}
scanNode = scanNode->next; //Moves the pointer forward to the next node
//Loop is entered through the second node and stops when scanNode takes the address of the
//first node through the last node
while(scanNode != firstNode){
if(scanNode->data == searchValue){ //If value is found in a node
valueFound = 1;
searchNode = scanNode;
}
scanNode = scanNode->next;
}
//Check if value is found or not
if (valueFound){
printf("Value is found \n");
}
else{
printf("Value not found\n");
}
return searchNode;
}
int getNodeValue(){ //Gets data to be stored in node from the user
int value;
printf("Enter value in node\n");
scanf("%d", &value);
return value;
}
void insertInList(){
struct nodeStructure *newNode;
int insertAnswer;
//Allocate memory for a node and pass it's address to newNode
newNode = Malloc(struct nodeStructure);
if (!firstNode){ //If the list doesn't exist
//Get value for node
newNode->data = getNodeValue();
//Initialize newNode as the first and last nodes
firstNode = newNode;
lastNode = firstNode;
//Initialize the node pointers to create a self referential node
newNode->next = lastNode;
newNode->previous = firstNode;
}
else{ //If the list exists
//Menu to display for insertion
system("cls");
printf("Insertion In Linked List\n");
printf("01. At the beginning\n");
printf("02. At the end\n");
printf("03. At a position\n");
scanf("%d", &insertAnswer);
//Switch case for user choice to insert node
switch (insertAnswer){
case 1: //Inserts a node at the beginning of the list
putNodeAtStart();
break;
case 2: //Inserts a node at the end of the list
putNodeAtEnd();
break;
case 3: //Inserts a node at a position given by the user
putNodeAtPosition();
break;
default:
break;
}
}
getch();
}
void putNodeAtStart(){
struct nodeStructure *newNode;
//Allocate memory for a node and pass it's address to newNode
newNode = Malloc(struct nodeStructure);
//Get value for node
newNode->data = getNodeValue();
//Placing the node in the circular doubly linked list at first position
newNode->next = firstNode;
firstNode->previous = newNode;
newNode->previous = lastNode;
lastNode->next = newNode;
firstNode = newNode;
}
void putNodeAtEnd(){
struct nodeStructure *newNode;
//Allocate memory for a node and pass it's address to newNode
newNode = Malloc(struct nodeStructure);
//Get value for node
newNode->data = getNodeValue();
//Placing the node in the doubly linked list at the end position
lastNode->next = newNode;
newNode->previous = lastNode;
newNode->next = firstNode;
firstNode->previous = newNode;
lastNode = newNode;
}
void putNodeAtPosition(){
struct nodeStructure *newNode, *searchNode;
//Get the node with the given search value
searchNode = searchInNodes();
if(searchNode != NULL){ //if search value is found
if(searchNode == lastNode){ //If the searched value is found in the last node
putNodeAtEnd();
}
else if(searchNode ==firstNode){ //If the searched value is found in the first node
putNodeAtStart();
}
else{
//Allocate memory for a node and pass it's address to newNode
newNode = Malloc(struct nodeStructure);
//Get value for node
newNode->data = getNodeValue();
//Attaches the new node after the search node
newNode->next = searchNode->next;
searchNode->next = newNode;
newNode->previous = searchNode;
//Traverse both the nodes forward to create reverse linkage to the newNode by the node after the searched node
searchNode = searchNode->next;
newNode = newNode->next;
newNode->previous = searchNode;
}
}
else{ //if search value isn't found exit the current function
return;
}
}
void deleteFromList(){
int insertAnswer;
if (!firstNode){ //If the list doesn't exist
printf("No nodes exist underflow\n");
}
else{ //If the list exists
//Menu to display for insertion
system("cls");
printf("Deletion In Linked List\n");
printf("01. At the beginning\n");
printf("02. At the end\n");
printf("03. At a position\n");
scanf("%d", &insertAnswer);
//Switch case for user choice to insert node
switch (insertAnswer){
case 1: //Remove the first node in linked list
removeNodeFromStart();
break;
case 2: //Removes last node from linked list
removeNodeFromEnd();
break;
case 3: //Removes node at a position given by the user
removeNodeAtPosition();
break;
default:
break;
}
}
getch();
}
void removeNodeFromStart(){
//initialize a new node to store address of node to be deleted
struct nodeStructure *deleteNode;
deleteNode = firstNode;
//Make the second node the first node and delete the original first node
firstNode = firstNode->next;
firstNode->previous = lastNode;
lastNode->next = firstNode; //Attaches the last node to the new first node
free(deleteNode); //frees the memory space
printf("Node deleted successfully\n");
}
void removeNodeFromEnd(){
//initialize a new node to store address of node to be deleted
struct nodeStructure *deleteNode;
//Makes the second last node as the last node and deletes the original last node
deleteNode = lastNode;
lastNode = lastNode->previous;
lastNode->next = firstNode;
firstNode->previous = lastNode; //Attaches the first node to the new last node
free(deleteNode); //frees the memory space
printf("Node deleted successfully\n");
}
void removeNodeAtPosition(){
//initialize a new node to store address of node to be deleted, the node before it and after it
struct nodeStructure *deleteNode, *previousNode, *nextNode;
//Get the node with the search value
deleteNode = searchInNodes();
if(deleteNode != NULL){ //If the search value is found
if(deleteNode == lastNode){
removeNodeFromEnd();
return;
}
else if(deleteNode == firstNode){
removeNodeFromStart();
return;
}
else{
previousNode = deleteNode->previous; //initialize the previous node
//Break connections from the node to be deleted
previousNode->next = deleteNode->next;
nextNode = deleteNode->next;
nextNode->previous = previousNode;
free(deleteNode); //frees the memory space
printf("Node deleted successfully\n");
}
}
else{
return;
}
}
void getNodes(){ //Displays the list using double arrow connections
struct nodeStructure *scanNode;
scanNode = firstNode;
if(firstNode){
printf("The linked list is \n");
printf("HEAD");
printf(" < -- > %d", firstNode->data);
scanNode = firstNode->next;
//Loop is entered through the second node and stops when scanNode takes the address of the
//first node through the last node
while (scanNode != firstNode){
printf(" < -- > %d",scanNode->data);
scanNode = scanNode->next;
}
printf(" < -- > HEAD"); //Last node points to NULL
}
else{
printf("List is empty, No nodes found\n");
}
getch();
}
//Written in ANSI C for the GNU-GCC compiler
//Elit Altum