Nested structures in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested struct member access

What is the output of this C++ code?

C++

struct Point {
    int x;
    int y;
};

struct Rectangle {
    Point topLeft;
    Point bottomRight;
};

#include <iostream>
int main() {
    Rectangle rect = {{1, 4}, {5, 1}};
    std::cout << rect.topLeft.x << "," << rect.bottomRight.y << std::endl;
    return 0;
}

A 1,4

B 5,4

C 5,1

D 1,1

💡 Hint

Look at how the nested points are initialized and which members are accessed.

The Rectangle struct has two Points: topLeft and bottomRight. topLeft.x is 1, bottomRight.y is 1, so output is '1,1'.

❓ Predict Output

intermediate

Output of nested struct with array member

What will this program print?

C++

struct Team {
    struct Player {
        int id;
        int score;
    } players[3];
};

#include <iostream>
int main() {
    Team team = {{{1, 10}, {2, 20}, {3, 30}}};
    std::cout << team.players[1].score << std::endl;
    return 0;
}

A 10

B 20

C 30

D 1

💡 Hint

Check which player index is accessed and which member is printed.

players[1] is the second player with id=2 and score=20, so output is 20.

🔧 Debug

advanced

Identify the error in nested struct initialization

This code tries to initialize nested structs but causes a compilation error. What is the error?

C++

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

struct Event {
    char name[20];
    Date date;
};

int main() {
    Event e = {"Meeting", {12, 5}};
    return 0;
}

A Struct Event cannot contain another struct

B Cannot initialize char array with string literal

C Missing year value in nested Date initialization

D Missing semicolon after struct definitions

💡 Hint

Check how many values are needed to initialize Date.

Date requires three integers (day, month, year), but only two are provided, causing a compilation error.

📝 Syntax

advanced

Correct syntax to access nested struct member

Which option correctly accesses the 'z' member inside nested structs?

C++

struct Inner {
    int z;
};

struct Outer {
    Inner inner;
};

Outer o = {{5}};

A o.inner.z

B o->inner.z

C o.inner->z

D o->inner->z

💡 Hint

Remember the difference between dot (.) and arrow (->) operators.

o is an object, so use dot operator to access members. Arrow operator is for pointers.

🚀 Application

expert

Calculate total price from nested structs

Given the structs below, what is the total price printed by the program?

C++

struct Item {
    char name[10];
    int quantity;
    double price_per_unit;
};

struct Order {
    Item items[2];
};

#include <iostream>
int main() {
    Order order = {{{"Pen", 10, 1.5}, {"Notebook", 5, 3.0}}};
    double total = 0;
    for (int i = 0; i < 2; ++i) {
        total += order.items[i].quantity * order.items[i].price_per_unit;
    }
    std::cout << total << std::endl;
    return 0;
}

A 30

B 25

C 20

D 35

💡 Hint

Multiply quantity by price for each item and add them up.

Pen: 10 * 1.5 = 15, Notebook: 5 * 3.0 = 15, total = 30.0

Practice

1. What is the main purpose of using nested structures in C++?

easy

A. To allow structures to inherit functions

B. To create multiple inheritance between classes

C. To increase the size of a structure unnecessarily

D. To group related data logically inside another structure

Solution

1. Step 1: Understand nested structures concept

   Nested structures let you put one structure inside another to group related data logically.

2. Step 2: Compare options

   Only To group related data logically inside another structure correctly describes grouping data logically. Other options describe unrelated concepts.

3. Final Answer:

   To group related data logically inside another structure -> Option D

4. Quick Check:

   Nested structures = group data logically [OK]

Hint: Think of nested structures as folders inside folders [OK]

Common Mistakes:

• Confusing nested structures with inheritance
• Thinking nested structures increase structure size unnecessarily
• Assuming nested structures add functions

2. Which of the following is the correct syntax to access member city inside a nested structure address within person?

easy

A. person->address.city

B. person.address.city

C. person.address->city

D. person->address->city

Solution

1. Step 1: Identify access operator for nested structures

   When accessing members of nested structures by variable (not pointer), use dot operator for each level.

2. Step 2: Apply to given example

   Since person is a variable, access address with dot, then city with dot: person.address.city.

3. Final Answer:

   person.address.city -> Option B

4. Quick Check:

   Use dot for nested struct members when variable, not pointer [OK]

Hint: Use dot operator for nested struct members if not pointers [OK]

Common Mistakes:

• Using arrow operator (->) when variable is not a pointer
• Mixing dot and arrow operators incorrectly
• Trying to access nested member directly without parent

3. What will be the output of the following code?

struct Date {
  int day;
  int month;
};
struct Event {
  char name[10];
  Date date;
};

int main() {
  Event e = {"Party", {25, 12}};
  std::cout << e.name << " on " << e.date.day << "/" << e.date.month << std::endl;
  return 0;
}

medium

A. Party on 25/12

B. Party on 12/25

C. Compilation error

D. Party on 0/0

Solution

1. Step 1: Understand structure initialization

   Event e is initialized with name "Party" and Date with day=25, month=12.

2. Step 2: Trace output statement

   Output prints e.name, then e.date.day (25), then e.date.month (12) separated by slashes.

3. Final Answer:

   Party on 25/12 -> Option A

4. Quick Check:

   Nested struct initialized correctly = Party on 25/12 [OK]

Hint: Match initialization order with nested structure fields [OK]

Common Mistakes:

• Swapping day and month values
• Assuming compilation error due to nested struct
• Forgetting to use dot operator to access nested members

4. Identify the error in the following code snippet:

struct Point {
  int x, y;
};
struct Rectangle {
  Point topLeft;
  Point bottomRight;
};

int main() {
  Rectangle rect;
  rect.topLeft->x = 0;
  rect.topLeft->y = 10;
  return 0;
}

medium

A. Using arrow operator (->) on a non-pointer structure variable

B. Missing semicolon after struct definitions

C. Incorrect member names in Rectangle

D. Rectangle struct cannot contain Point structs

Solution

1. Step 1: Check member access operators

   rect.topLeft is a structure variable, not a pointer, so dot operator (.) must be used, not arrow (->).

2. Step 2: Identify error cause

   Using -> on non-pointer causes compilation error.

3. Final Answer:

   Using arrow operator (->) on a non-pointer structure variable -> Option A

4. Quick Check:

   Use dot for struct variables, arrow for pointers [OK]

Hint: Use dot for struct variables, arrow only for pointers [OK]

Common Mistakes:

• Confusing dot and arrow operators
• Assuming arrow works for all struct members
• Ignoring compiler error messages

5. Given the following nested structures, how would you write a function printBookInfo that prints the book title and the author's city?

struct Author {
  char name[50];
  char city[30];
};
struct Book {
  char title[100];
  Author author;
};

hard

A. void printBookInfo(Book b) { std::cout << b.title << ", " << b.author->city << std::endl; }

B. void printBookInfo(Book b) { std::cout << b.title << ", " << b.city << std::endl; }

C. void printBookInfo(Book b) { std::cout << b.title << ", " << b.author.city << std::endl; }

D. void printBookInfo(Book b) { std::cout << b->title << ", " << b->author.city << std::endl; }

Solution

1. Step 1: Understand structure member access

   Book variable b has member title and nested structure author. Access author.city with dot operator.

2. Step 2: Check each option

   void printBookInfo(Book b) { std::cout << b.title << ", " << b.author.city << std::endl; } correctly uses b.title and b.author.city with dot operators. Others misuse arrow or omit author.

3. Final Answer:

   void printBookInfo(Book b) { std::cout << b.title << ", " << b.author.city << std::endl; } -> Option C

4. Quick Check:

   Access nested struct members with dot: b.author.city [OK]

Hint: Use dot operator for nested struct members in function parameters [OK]

Common Mistakes:

• Using arrow operator on non-pointer parameter
• Skipping nested struct name when accessing member
• Using pointer syntax incorrectly