How to write a C Program to create a Hash table taking in student name, class and total marks; display students' details based on class; search based on student's name and Display highest marks in the class in C Programming Language ?
Hash tables are commonly used because of their speed searching takes on average constant time, whereas trees take logarithmic time, and linked lists searching takes linear time.https://en.wikipedia.org/wiki/Hash_table
Solution:
/* Hash table taking in student name, class and total marks; display students' details based on class; search based on student's name and Display highest marks in the class */
//Implementation of a Hash Table to store information about a student.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SIZE 10
struct hash {
char name[20];
float marks;
int class;
struct hash* ptr;
};
struct hash *DICT[SIZE];
void makenull()
{
int i;
for(i=1; i<=SIZE; i++)
{
DICT[i]=NULL;
}
}
int hash(int class)
{
return(class%SIZE);
}
void insert()
{
char nam[20];
float mar;
int cl,i,index;
struct hash *oldptr;
printf("Enter the student name\n");
scanf("%s",nam);
printf("Enter the marks\n");
scanf("%f", &mar);
printf("Enter the class\n");
scanf("%d",&cl);
index=hash(cl);
oldptr = DICT[index];
DICT[index]= (struct hash *) malloc(sizeof (struct hash));
// DICT[index]->name[20]=nam[20];
strcpy(DICT[index]->name, nam);
DICT[index]->marks=mar;
DICT[index]->class=cl;
DICT[index]->ptr=oldptr;
}
void display()
{
int index,class,count;
struct hash *head;
printf("Enter the students class to display\n");
scanf("%d",&class);
count=0;
index=hash(class);
head= DICT[index];
while (head != NULL)
{
printf("Name: %s\n",head->name);
printf("Class: %d\n", head->class);
printf("Marks: %f\n\n", head->marks);
count++;
head = head->ptr;
}
printf("The count of students in this class are: %d\n", count);
}
void search()
{
int index,class;
char ename[20];
struct hash *head;
printf("Enter the students class to display\n");
scanf("%d",&class);
index=hash(class);
head= DICT[index];
printf("Enter the student's name to be searched\n");
scanf("%s",ename);
while (head != NULL )
{
if(! strcmp(head->name, ename))
{
printf("The name is: %s\n",head->name);
printf("The class is: %d\n", head->class);
printf("The marks are: %f\n", head->marks);
break;
}
else{
if (head != NULL)
{
head=head->ptr;
}
else
printf("Student not found\n");
}
}
}
void high()
{
int index,class;
float high;
struct hash *head;
printf("Enter the students class to check marks\n");
scanf("%d",&class);
index=hash(class);
head= DICT[index];
while (head != NULL)
{
if(head->ptr != NULL)
{
if((head->marks) > (head->ptr->marks))
{
high=head->marks;
}
else
{
high=head->ptr->marks;
}
}
if(head->ptr != NULL)
head=head->ptr;
else{
printf("The highest marks in the class are: %f\n", high);
break;
}
}
}
int main ()
{
int num,i,choice;
printf("Enter the number of students' details you want to enter\n");
scanf("%d",&num);
makenull();
for(i=0; i<num; i++)
{
insert();
}
printf("What do you want to do now\n");
do {
printf("Enter your choice\n");
printf("1->Display\n2->Search \n3->Find Highest\n4->Exit\n");
scanf("%d",&choice);
switch(choice)
{
case 1: display();
break;
case 2: search();
break;
case 3: high();
break;
case 4: exit(0);
}
} while ( choice != 4);
return 0;
}