`luc113.c`¶

Problem Statement

Store date in a structure using bit fields (day: 5 bits, month: 4 bits, year: 12 bits). Read joining dates of 10 employees and display them sorted by year.

Metadata¶

Property	Detail
Author	Amit Dutta amitdutta4255@gmail.com
Date	08 Feb 2026
License	MIT License (See the LICENSE file for details)
Difficulty	Intermediate (index: 4 / 10)

Concepts¶

Beta Feature

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Array
Pointers
Sorting
Iteration
Recursion

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Source Code¶

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// Define structure with bit-fields
struct date
{
    unsigned int day : 5;   // 1-31 takes 5 bits
    unsigned int month : 4; // 1-12 takes 4 bits
    unsigned int year : 12; // Sufficient for year 0-4095
};

struct employee
{
    char name[30];
    struct date doj; // Date of Joining
};

int compare_dates(const void *a, const void *b);

int main()
{
    struct employee emp[10];
    int i;
    // Temporary variables for input because we cannot take address of a bit-field
    int d, m, y; 

    printf("Enter details for 10 employees:\n");
    for (i = 0; i < 10; i++)
    {
        printf("\nEmployee %d Name: ", i + 1);
        scanf("%s", emp[i].name);

        printf("Date of Joining (dd mm yyyy): ");
        scanf("%d %d %d", &d, &m, &y);

        // Assign to bit-fields
        emp[i].doj.day = d;
        emp[i].doj.month = m;
        emp[i].doj.year = y;
    }

    // Sort based on year using qsort
    qsort(emp, 10, sizeof(struct employee), compare_dates);

    printf("\n--- Employees Sorted by Joining Year ---\n");
    for (i = 0; i < 10; i++)
    {
        printf("%-15s | DOJ: %02d-%02d-%d\n", 
               emp[i].name, emp[i].doj.day, emp[i].doj.month, emp[i].doj.year);
    }

    return 0;
}

int compare_dates(const void *a, const void *b)
{
    struct employee *e1 = (struct employee *)a;
    struct employee *e2 = (struct employee *)b;

    // Primary sort by Year
    if (e1->doj.year != e2->doj.year)
        return e1->doj.year - e2->doj.year;

    // Secondary sort by Month
    if (e1->doj.month != e2->doj.month)
        return e1->doj.month - e2->doj.month;

    // Tertiary sort by Day
    return e1->doj.day - e2->doj.day;
}

Explanation¶

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    - Only use the given code. Do NOT assume anything not present.

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    - Keep explanation clear and short.

    - If something is unclear, say "Not clear from code".

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    FORMAT:

    [START]

    ## What it does

    (Explain the overall purpose in 1-2 sentences)

    ## Step-by-step

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    ## Key Concepts

    (List concepts like loop, condition, function, etc.)

    ## Notes

    (Mention any limitations, errors, or assumptions)

    [END]

    CODE (luc113.c):

    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>

    // Define structure with bit-fields
    struct date
    {
        unsigned int day : 5;   // 1-31 takes 5 bits
        unsigned int month : 4; // 1-12 takes 4 bits
        unsigned int year : 12; // Sufficient for year 0-4095
    };

    struct employee
    {
        char name[30];
        struct date doj; // Date of Joining
    };

    int compare_dates(const void *a, const void *b);

    int main()
    {
        struct employee emp[10];
        int i;
        // Temporary variables for input because we cannot take address of a bit-field
        int d, m, y; 

        printf("Enter details for 10 employees:\n");
        for (i = 0; i < 10; i++)
        {
            printf("\nEmployee %d Name: ", i + 1);
            scanf("%s", emp[i].name);

            printf("Date of Joining (dd mm yyyy): ");
            scanf("%d %d %d", &d, &m, &y);

            // Assign to bit-fields
            emp[i].doj.day = d;
            emp[i].doj.month = m;
            emp[i].doj.year = y;
        }

        // Sort based on year using qsort
        qsort(emp, 10, sizeof(struct employee), compare_dates);

        printf("\n--- Employees Sorted by Joining Year ---\n");
        for (i = 0; i < 10; i++)
        {
            printf("%-15s | DOJ: %02d-%02d-%d\n", 
                   emp[i].name, emp[i].doj.day, emp[i].doj.month, emp[i].doj.year);
        }

        return 0;
    }

    int compare_dates(const void *a, const void *b)
    {
        struct employee *e1 = (struct employee *)a;
        struct employee *e2 = (struct employee *)b;

        // Primary sort by Year
        if (e1->doj.year != e2->doj.year)
            return e1->doj.year - e2->doj.year;

        // Secondary sort by Month
        if (e1->doj.month != e2->doj.month)
            return e1->doj.month - e2->doj.month;

        // Tertiary sort by Day
        return e1->doj.day - e2->doj.day;
    }

luc113.c¶