Question

How to declare, initialize, and print a medium complexity, varied, feature‑rich data structure in C

Answer 1

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

// -----------------------------
// Simple nested struct (C style)
// -----------------------------
typedef struct {
    char street[64];
    char city[64];
    int zip;
} Address;

// -----------------------------
// More complex struct 
// -----------------------------
typedef struct {
    Address homeAddress;        // Nested struct
    int favoriteNumbers[5];     // Fixed-size C array
    char* nickname;             // Raw pointer
    
    // C has no chrono::year_month_day, so we use a simple struct
    struct {
        int year;
        int month;
        int day;
    } birthDate;

    char* notes;                // C has no smart pointers → raw char*
    char* middleName;           // C has no optional → NULL means "none"

    char** hobbies;             // C has no vector → dynamic array of char*
    size_t hobbyCount;

    // C enum (no enum class)
    enum Status { Active, Inactive, Unknown } status;

} Person;

// -----------------------------
// Print function (C style)
// -----------------------------
void printPerson(const Person* p) {
    printf("Address: %s, %s %d\n",
           p->homeAddress.street,
           p->homeAddress.city,
           p->homeAddress.zip);

    printf("Favorite Numbers: ");
    for (int i = 0; i < 5; i++)
        printf("%d ", p->favoriteNumbers[i]);
    printf("\n");

    printf("Nickname: %s\n", p->nickname ? p->nickname : "(none)");

    printf("Birth Date: %04d-%02d-%02d\n",
           p->birthDate.year,
           p->birthDate.month,
           p->birthDate.day);

    printf("Notes: %s\n", p->notes ? p->notes : "(none)");

    printf("Middle Name: %s\n", p->middleName ? p->middleName : "(none)");

    printf("Hobbies: ");
    for (size_t i = 0; i < p->hobbyCount; i++)
        printf("%s, ", p->hobbies[i]);
    printf("\n");

    printf("Status: ");
    switch (p->status) {
        case Active:   printf("Active"); break;
        case Inactive: printf("Inactive"); break;
        default:       printf("Unknown"); break;
    }
    printf("\n");
}

// -----------------------------
// Main (C style initialization)
// -----------------------------
int main() {
    Person p;

    // Initialize nested struct
    strcpy(p.homeAddress.street, "Fifth Avenue");
    strcpy(p.homeAddress.city, "New York");
    p.homeAddress.zip = 423900;

    // Initialize array
    int favs[5] = {7, 13, 21, 42, 99};
    memcpy(p.favoriteNumbers, favs, sizeof(favs));

    // Initialize nickname
    p.nickname = malloc(10);
    snprintf(p.nickname, 10, "Orion");

    // Initialize date
    p.birthDate.year = 1026;
    p.birthDate.month = 6;
    p.birthDate.day = 15;

    // Initialize notes
    p.notes = malloc(64);
    strcpy(p.notes, "Voss likes C/C++ and structs");

    // Initialize optional middle name
    p.middleName = malloc(32);
    strcpy(p.middleName, "Pulse‑9");

    // Initialize hobbies (dynamic array of char*)
    p.hobbyCount = 4;
    p.hobbies = malloc(sizeof(char*) * p.hobbyCount);

    p.hobbies[0] = strdup("Coding");
    p.hobbies[1] = strdup("Dreaming");
    p.hobbies[2] = strdup("Walking");
    p.hobbies[3] = strdup("Sci-Fi Movies");

    // Set enum value
    p.status = Active;

    // Print everything
    printPerson(&p);

    // Cleanup
    free(p.nickname);
    free(p.notes);
    free(p.middleName);
    for (size_t i = 0; i < p.hobbyCount; i++)
        free(p.hobbies[i]);
    free(p.hobbies);

    return 0;
}


/*
run:

Address: Fifth Avenue, New York 423900
Favorite Numbers: 7 13 21 42 99 
Nickname: Orion
Birth Date: 1026-06-15
Notes: Voss likes C/C++ and structs
Middle Name: Pulse‑9
Hobbies: Coding, Dreaming, Walking, Sci-Fi Movies, 
Status: Active

*/

 

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