Data Structure: Linked List

LinkedList.cpp

//Linked list operations
//Author: Milon

#include<stdio.h>
#include<string.h>
#include<malloc.h>
//#include<conio.h>

void insert_first();
void insert_last();
void insert_before();
void insert_after();
void search_list();
void delete_node();
void show_list();

struct student{
    char name[25];
    char roll[8];
    char dept[4];
    char semester[10];
    struct student *next;
    } *start=NULL;

void main(){
    int d=0;
    char choice;
    do{
        //clrscr();
        printf("This program is for Linked List operations.\n\n");
        printf("# Insert at (F)irst position.\n");
        printf("# Insert at (L)ast position.\n");
        printf("# Insert (B)efore node.\n");
        printf("# Insert (A)fter node.\n");
        printf("# (S)earch in a list.\n");
        printf("# (R)emove a node from list.\n");
        printf("# (D)isplay all nodes of list.\n");
        printf("# (E)xit\n\n\n");
        printf("Enter your choice: ");
        choice=getchar();
        switch(choice){
            case 'F':
            case 'f':
                insert_first();
                break;
            case 'L':
            case 'l':
                insert_last();
                break;
            case 'B':
            case 'b':
                insert_before();
                break;
            case 'A':
            case 'a':
                insert_after();
                break;
            case 'S':
            case 's':
                search_list();
                break;
            case 'R':
            case 'r':
                delete_node();
                break;
            case 'D':
            case 'd':
                show_list();
                break;
            case 'E':
            case 'e':
                d=1;
                break;
            default:
                printf("\nInvalid input.");
                break;
            }
        }while(d==0);
    }

void insert_first(){
    struct student *data;
    data=(struct student*)malloc(sizeof(struct student));
    printf("\nEnter your name: ");
    gets(data->name);
    printf("\nEnter your roll: ");
    gets(data->roll);
    printf("\nEnter your department: ");
    gets(data->dept);
    printf("\nEnter your semester: ");
    gets(data->semester);
    data->next=NULL;
    if(start==NULL)
        start=data;
    else{
        data->next=start;
        start=data;
        }
    printf("\nItem successfully inserted.");
    //getch();
    }

void insert_last(){
    struct student *data,*ptr;
    data=(struct student*)malloc(sizeof(struct student));
    printf("\nEnter your name: ");
    gets(data->name);
    printf("\nEnter your roll: ");
    gets(data->roll);
    printf("\nEnter your department: ");
    gets(data->dept);
    printf("\nEnter your semester: ");
    gets(data->semester);
    data->next=NULL;
    if(start==NULL)
        start=data;
    else{
        ptr=start;
        while(ptr->next!=NULL)
            ptr=ptr->next;
        ptr->next=data;
        }
    printf("\nItem successfully inserted.");
    //getch();
    }

void insert_before(){
    char roll[8];
    struct student *data,*prev,*ptr;
    printf("\nEnter the student roll before which you want to insert: ");
    gets(roll);
    ptr=start;
    while(strcmp(roll,ptr->roll)!=0&&ptr!=NULL)
        ptr=ptr->next;
    if(ptr==NULL){
        printf("\Item not found.");
        //getch();
        return;
        }
    data=(struct student*)malloc(sizeof(struct student));
    printf("\nEnter your name: ");
    gets(data->name);
    printf("\nEnter your roll: ");
    gets(data->roll);
    printf("\nEnter your department: ");
    gets(data->dept);
    printf("\nEnter your semester: ");
    gets(data->semester);
    data->next=NULL;
    ptr=start;
    if(strcmp(roll,ptr->roll)==0){
        ptr->next=start;
        start=ptr;
        }
    else{
        ptr=ptr->next;
        prev=start;
        while(strcmp(roll,ptr->roll)!=0){
            ptr=ptr->next;
            prev=prev->next;
            }
        }
    data->next=ptr;
    prev->next=data;
    printf("\nItem successfully Inserted.");
    //getch();
    }

void insert_after(){
    char roll[8];
    struct student *data,*ptr;
    printf("\nEnter the student roll before which you want to insert: ");
    gets(roll);
    ptr=start;
    while(strcmp(roll,ptr->roll)!=0&&ptr!=NULL)
        ptr=ptr->next;
    if(ptr==NULL){
        printf("\Item not found.");
        //getch();
        return;
        }
    data=(struct student*)malloc(sizeof(struct student));
    printf("\nEnter your name: ");
    gets(data->name);
    printf("\nEnter your roll: ");
    gets(data->roll);
    printf("\nEnter your department: ");
    gets(data->dept);
    printf("\nEnter your semester: ");
    gets(data->semester);
    data->next=NULL;
    ptr=start;
    while(strcmp(roll,ptr->roll)!=0)
        ptr=ptr->next;
    data->next=ptr->next;
    ptr->next=data;
    printf("\nItem successfully inserted.");
    //getch();
    }

void search_list(){
    char roll[8];
    struct student *ptr;
    printf("\nEnter the student roll you want to search: ");
    gets(roll);
    ptr=start;
    while(strcmp(roll,ptr->roll)!=0&&ptr->next!=NULL)
        ptr=ptr->next;
    if(ptr->next==NULL)
        printf("\nNo match found.");
    else{
        printf("\nItem found.\n");
        printf("%28s %10s %5s %12s",ptr->name,ptr->roll,ptr->dept,ptr->semester);
        }
    //getch();
    }

void delete_node(){
    char roll[8];
    struct student *ptr,*prev;
    printf("\nEnter the student roll you want to search: ");
    gets(roll);
    ptr=start;
    if(strcmp(ptr->roll,roll)==0)
        start=ptr->next;
    else{
        ptr=ptr->next;
        prev=start;
        while(strcmp(roll,ptr->roll)!=0&&ptr->next!=NULL){
            ptr=ptr->next;
            prev=prev->next;
            }
        if(ptr->next==NULL)
            printf("No match found.");
        else
            prev->next=ptr->next;
        }
    printf("\nNode is successfully deleted.");
    //getch();
    }

void show_list(){
    int c=0;
    struct student *ptr;
    if(start==NULL)
        printf("List is empty.");
    else{
        ptr=start;
        while(ptr!=NULL){
            printf("\n%3d.%25s%10s%5s%12s",++c,ptr->name,ptr->roll,ptr->dept,ptr->semester);
            ptr=ptr->next;
            }
        }
    //getch();
    }