C program to store Student records as Structures and Sort them by Age or ID

Given student’s records with each record containing id, name and age of a student. Write a C program to read these records and display them in sorted order by age or id.

Sorting by Age

Examples:

Input: Student Records = {
{Id = 1, Name = bd, Age = 12 },
{Id = 2, Name = ba, Age = 10 },
{Id = 3, Name = bc, Age = 8 },
{Id = 4, Name = aaz, Age = 9 },
{Id = 5, Name = az, Age = 10 } }

Output:
{{Id = 3, Name = bc, Age = 8 },
{Id = 4, Name = aaz, Age = 9 },
{Id = 2, Name = ba, Age = 10 },
{Id = 5, Name = az, Age = 10 },
{Id = 1, Name = bd, Age = 12 } }

Approach: This problem is solved in the following steps:

Create a structure with fields id, name and age.
Read the students records in the structure
Define a comparator by setting up rules for comparison. Here age can be sorted with the help of difference of the age of 2 students. (Student1 -> age – Student2 -> age)
Now sort the structure based on the defined comparator with the help of qsort() method.
Print the sorted students’ records.

Program:

// C program to read Student records 
// like id, name and age, 
// and display them in sorted order by Age 
  
#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
  
// struct person with 3 fields 
struct Student { 
    char* name; 
    int id; 
    char age; 
}; 
  
// setting up rules for comparison 
// to sort the students based on age 
int comparator(const void* p, const void* q) 
{ 
    return (((struct Student*)p)->age - ((struct Student*)q)->age); 
} 
  
// Driver program 
int main() 
{ 
    int i = 0, n = 5; 
  
    struct Student arr[n]; 
  
    // Get the students data 
    arr[0].id = 1; 
    arr[0].name = "bd"; 
    arr[0].age = 12; 
  
    arr[1].id = 2; 
    arr[1].name = "ba"; 
    arr[1].age = 10; 
  
    arr[2].id = 3; 
    arr[2].name = "bc"; 
    arr[2].age = 8; 
  
    arr[3].id = 4; 
    arr[3].name = "aaz"; 
    arr[3].age = 9; 
  
    arr[4].id = 5; 
    arr[4].name = "az"; 
    arr[4].age = 10; 
  
    // Print the Unsorted Structure 
    printf("Unsorted Student Records:\n"); 
    for (i = 0; i < n; i++) { 
        printf("Id = %d, Name = %s, Age = %d \n", 
               arr[i].id, arr[i].name, arr[i].age); 
    } 
    // Sort the structure 
    // based on the specified comparator 
    qsort(arr, n, sizeof(struct Student), comparator); 
  
    // Print the Sorted Structure 
    printf("\n\nStudent Records sorted by Age:\n"); 
    for (i = 0; i < n; i++) { 
        printf("Id = %d, Name = %s, Age = %d \n", 
               arr[i].id, arr[i].name, arr[i].age); 
    } 
  
    return 0; 
} 

Output:

Unsorted Student Records:
Id = 1, Name = bd, Age = 12 
Id = 2, Name = ba, Age = 10 
Id = 3, Name = bc, Age = 8 
Id = 4, Name = aaz, Age = 9 
Id = 5, Name = az, Age = 10 


Student Records sorted by Age:
Id = 3, Name = bc, Age = 8 
Id = 4, Name = aaz, Age = 9 
Id = 2, Name = ba, Age = 10 
Id = 5, Name = az, Age = 10 
Id = 1, Name = bd, Age = 12

Sorting by Id