Nested structures - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested struct member access

What is the output of this C code snippet?

C

typedef struct {
    int x;
    int y;
} Point;

typedef struct {
    Point topLeft;
    Point bottomRight;
} Rectangle;

#include <stdio.h>

int main() {
    Rectangle rect = {{1, 2}, {3, 4}};
    printf("%d\n", rect.bottomRight.x);
    return 0;
}

A 2

B 4

C 3

D 1

💡 Hint

Look at how the nested structs are initialized and accessed.

The Rectangle struct has two Point members: topLeft and bottomRight. The code prints rect.bottomRight.x, which is initialized to 3.

❓ Predict Output

intermediate

Value of nested struct after assignment

What is the value of p2.y after this code runs?

C

typedef struct {
    int x;
    int y;
} Point;

#include <stdio.h>

int main() {
    Point p1 = {5, 10};
    Point p2;
    p2 = p1;
    p2.y = 20;
    printf("%d\n", p2.y);
    return 0;
}

A 20

B 5

C 10

D 0

💡 Hint

Remember that assigning structs copies all members.

p2 is assigned p1, then p2.y is changed to 20, so printing p2.y outputs 20.

❓ Predict Output

advanced

Output of nested struct pointer access

What does this program print?

C

typedef struct {
    int id;
    struct {
        int day;
        int month;
        int year;
    } date;
} Event;

#include <stdio.h>

int main() {
    Event e = {101, {15, 8, 2023}};
    Event *ptr = &e;
    printf("%d-%d-%d\n", ptr->date.day, ptr->date.month, ptr->date.year);
    return 0;
}

A 101-15-8

B 15-8-2023

C 8-15-2023

D 2023-8-15

💡 Hint

Use the arrow operator to access nested struct members through a pointer.

The pointer ptr points to e. Accessing ptr->date.day etc. prints the date in day-month-year order.

❓ Predict Output

advanced

Result of modifying nested struct via pointer

What is the output of this program?

C

typedef struct {
    int x;
    int y;
} Point;

typedef struct {
    Point center;
    int radius;
} Circle;

#include <stdio.h>

int main() {
    Circle c = {{0, 0}, 5};
    Circle *pc = &c;
    pc->center.x = 10;
    printf("%d\n", c.center.x);
    return 0;
}

A 10

B 0

C Compilation error

D 5

💡 Hint

Changing a nested struct member via pointer affects the original struct.

The pointer pc points to c. Changing pc->center.x changes c.center.x to 10.

❓ Predict Output

expert

Output of complex nested struct initialization and access

What is the output of this program?

C

typedef struct {
    int day;
    int month;
    int year;
} Date;

typedef struct {
    char name[20];
    Date birthdate;
} Person;

#include <stdio.h>

int main() {
    Person people[2] = {
        {"Alice", {1, 1, 2000}},
        {"Bob", {31, 12, 1999}}
    };
    printf("%s was born on %d/%d/%d\n", people[1].name, people[1].birthdate.day, people[1].birthdate.month, people[1].birthdate.year);
    return 0;
}

A Alice was born on 31/12/1999

B Alice was born on 1/1/2000

C Bob was born on 1/1/2000

D Bob was born on 31/12/1999

💡 Hint

Check the array index and nested struct initialization carefully.

people[1] refers to the second element, Bob, with birthdate 31/12/1999.