Circular Linked List in C- royalarun.blogspot.com

Circular Linked List in C

#include "stdio.h"
#include "conio.h"
#include "stdlib.h"
#include "string.h"

/***** Structure template *****/
struct list{
int roll_no;
char name[20];
float marks;
struct list *next;
};

/***** Redefining struct list as node *****/
typedef struct list node;

void init(node*);
void ins_aft(node*); /*** FUNCTION FOR DELETING A NODE AFTER ***/
node* ins_bef(node*); /*** FUNCTION FOR INSERTING A NODE BEFORE ***/
node* del(node*); /*** FUNCTION FOR DELETING A NODE ***/
void search(node*); /*** FUNCTION FOR SEARCHING CRITERIA INPUT ***/
void disp(node*); /*** FUNCTION DISPLAYING THE NODES ***/
void rollsrch(node*); /*** FUNCTION SEARCHING THROUGH ROLL NUMBER ***/
void namesrch(node*); /*** FUNCTION SEARCHING THROUGH NAME ***/
void marksrch(node*); /*** FUNCTION SEARCHING THROUGH MARKS ***/

/***** Main function *****/
void main()
{
node *head; /* HEAD OF THE LINK LIST */
char ch; /* Choice inputing varible */
int opt; /* Option inputing variable*/
static int flag=0; /* Unchanged after iniialization */
clrscr();
head=(node*)malloc(sizeof(node));
head->next=NULL; /* NULL is being over written in init function */
do
{
again:
printf("\nEnter your option\n");
printf("\n1. Initialize the node\n");
printf("\n2. Insert before a specified node\n");
printf("\n3. Insert after a specified node\n");
printf("\n4. Delete a particular node\n");
printf("\n5. Search the nodes\n");
printf("\n6. Display all the nodes\n");
scanf("%d",&opt);
if(flag==0 && opt!=1)
{
printf("\nNo. You must first initialize at least one node\n");
goto again;
}
if(flag==1 && opt==1)
{
printf("\nInitialisation can occur only once.\n");
printf("\nNow you can insert a node\n");
goto again;
}
if(opt==4 && head->next==head)
{
printf("\nYou cannot delete the one and only the single node\n");
goto again;
}
if(flag==0 && opt==1)
flag=1;
switch(opt)
{
case 1:
init(head);
break;
case 2:
head=ins_bef(head);
break;
case 3:
ins_aft(head);
break;
case 4:
head=del(head);
break;
case 5:
search(head);
break;
case 6:
disp(head);
break;
}
printf("\nDo you wish to continue[y/n]\n");
ch=(char)getche();
}while(ch=='Y' || ch=='y');

printf("\nPress any key to exit\n");
getch();
}

/***** Initialisation function *****/
void init(node *start)
{
printf("\nEnter Roll number\n");
scanf("%d",&start->roll_no);
printf("\nEnter the name\n");
fflush(stdin);
gets(start->name);
printf("\nEnter the marks\n");
scanf("%f",&start->marks);
start->next=start;
}

/***** Function for inserting before a particular node *****/
node* ins_bef(node *start)
{
int rno; /* Roll number for inserting a node*/
node *newnode; /* New inputed node*/
node *current; /* Node for travelling the linked list*/
newnode=(node*)malloc(sizeof(node));
current=start;
printf("\nEnter the roll number before which you want to insert a node\n");
scanf("%d",&rno);
init(newnode);
if(current->roll_no==rno)
{
newnode->next=start;
while(current->next!=start)
current=current->next;
current->next=newnode;
start=newnode;
return(start);
}
while(current->next!=start)
{
if(current->next->roll_no==rno)
{
newnode->next=current->next;
current->next=newnode;
return(start);
}
current=current->next;
}
/*
If the function does not return from any return statement.
There is no match to insert before the input roll number.
*/
printf("\nMatch not found\n");
return(start);
}

/***** Function for inserting after a particular node *****/
void ins_aft(node *start)
{
int rno; /* Roll number for inserting a node*/
int flag=0;
node *newnode; /* New inputed node*/
node *current; /* Node for travelling the linked list*/
newnode=(node*)malloc(sizeof(node));
printf("\nEnter the roll number after which you want to insert a node\n");
scanf("%d",&rno);
init(newnode);
current=start;
while(current->next!=start)
{
/*** Insertion checking for all nodes except last ***/
if(current->roll_no==rno)
{
newnode->next=current->next;
current->next=newnode;
flag=1;
}
current=current->next;
}
if(flag==0 && current->next==start && current->roll_no==rno)
{
/*** Insertion checking for last nodes ***/
newnode->next=current->next; /** start is copied in newnode->next**/
current->next=newnode;
flag=1;
}
if(flag==0 && current->next==start)
printf("\nNo match found\n");
}

/***** deletion function *****/
node* del(node *start)
{
int rno; /* Roll number for deleting a node*/
node *delnode; /* Node to be deleted */
node *current; /* Node for travelling the linked list*/
printf("\nEnter the roll number whose node you want to delete\n");
scanf("%d",&rno);
current=start;
if(current->roll_no==rno)
{
/*** Checking condition for deletion of first node ***/
delnode=current; /* Unnecessary step */
while(current->next!=start)
current=current->next;
current->next=start->next;
start=start->next;
free(delnode);
return(start);
}
else
{
while(current->next->next!=start)
{
/*** Checking condition for deletion of ***/
/*** all nodes except first and last node ***/
if(current->next->roll_no==rno)
{
delnode=current->next;
current->next=current->next->next;
free(delnode);
return(start);
}
current=current->next;
}
if(current->next->next==start && current->next->roll_no==rno)
{
/*** Checking condition for deletion of last node ***/
delnode=current->next;
free(delnode);
current->next=start;
return(start);
}
}
printf("\nMatch not found\n");
return(start);
}

void search(node *start)
{
int ch; /* Choice inputing variable */
printf("\nEnter the criteria for search\n");
printf("\n1. Roll number\n");
printf("\n2. Name\n");
printf("\n3. Marks\n");
scanf("%d",&ch);
switch(ch)
{
case 1:
rollsrch(start);
break;
case 2:
namesrch(start);
break;
case 3:
marksrch(start);
break;
default:
rollsrch(start);
}
}

/***** Search function searching the appropriate roll number *****/
void rollsrch(node *start)
{
int rno; /* Roll number to be searched */
node *current; /* Node for travelling the linked list*/
current=start;
printf("\nEnter the roll number to search\n");
scanf("%d",&rno);
while(current->next!=start)
{
if(current->roll_no==rno)
printf("\n %d %s %f\n",current->roll_no,current->name,current->marks);
current=current->next;
}
if(current->next==start && current->roll_no==rno)
printf("\n %d %s %f\n",current->roll_no,current->name,current->marks);
}

/***** Search function searching the appropriate name *****/
void namesrch(node *start)
{
char arr[20]; /* Name to be searched */
node *current; /* Node for travelling the linked list*/
current=start;
printf("\nEnter the name to search\n");
fflush(stdin);
gets(arr);
while(current->next!=start)
{
if(strcmp(current->name,arr)==NULL)
printf("\n %d %s %f\n",current->roll_no,current->name,current->marks);
current=current->next;
}
if(current->next==start && strcmp(current->name,arr)==NULL)
printf("\n %d %s %f\n",current->roll_no,current->name,current->marks);
}

/***** Search function searching the appropriate marks *****/
void marksrch(node *start)
{
float marks; /* Marks to be searched */
node *current; /* Node for travelling the linked list*/
current=start;
printf("\nEnter the marks to search\n");
scanf("%f",&marks);
while(current->next!=start)
{
if(current->marks==marks)
printf("\n %d %s %f\n",current->roll_no,current->name,current->marks);
current=current->next;
}
if(current->next==start && current->marks==marks)
printf("\n %d %s %f\n",current->roll_no,current->name,current->marks);
}

/***** Output displaying function *****/
void disp(node *start)
{
node *current; /* Node for travelling the linked list*/
current=start;
while(current->next!=start)
{
printf("\n %d %s %f",current->roll_no,current->name,current->marks);
current=current->next;
}
printf("\n %d %s %f",current->roll_no,current->name,current->marks);
}


//Circular Linked List in C