Nested structures - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a nested structure.

C

struct Point {
    int x;
    int y;
};

struct Rectangle {
    struct Point [1];
    struct Point bottomRight;
};

Drag options to blanks, or click blank then click option'

AtopRight

BtopLeft

Ccorner

Dpoint

Attempts:

3 left

💡 Hint

Common Mistakes

Using a generic name like 'point' instead of a descriptive one.

Forgetting to name the nested struct member.

The nested structure member is named 'topLeft' to represent the top-left corner point of the rectangle.

2fill in blank

medium

Complete the code to access the x coordinate of the topLeft point in a Rectangle variable.

C

struct Rectangle rect;
int x_coord = rect.[1].x;

Drag options to blanks, or click blank then click option'

AtopLeft

Bpoint

CbottomRight

Dcorner

Attempts:

3 left

💡 Hint

Common Mistakes

Accessing bottomRight instead of topLeft.

Trying to access x directly from rect without the nested member.

To access the x coordinate of the topLeft point, use rect.topLeft.x.

3fill in blank

hard

Fix the error in the code to correctly initialize a nested structure.

C

struct Rectangle rect = { { [1], 10 }, {20, 30} };

Drag options to blanks, or click blank then click option'

A{5}

BtopLeft

C5

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using the member name instead of a value.

Using braces incorrectly around a single integer.

The nested Point is initialized with two integers. The first integer is 5 for x coordinate.

4fill in blank

hard

Fill both blanks to declare and initialize a nested structure variable.

C

struct Rectangle [1] = { {10, [2], {20, 30} };

Drag options to blanks, or click blank then click option'

Arect

B15

C25

Dbox

Attempts:

3 left

💡 Hint

Common Mistakes

Using an invalid variable name.

Confusing the y coordinate value.

The variable name is 'rect' and the y coordinate of topLeft is 15.

5fill in blank

hard

Fill all three blanks to define a nested structure and assign values.

C

struct Point {
    int [1];
    int [2];
};

struct Rectangle {
    struct Point topLeft;
    struct Point [3];
};

Drag options to blanks, or click blank then click option'

Ax

By

CbottomRight

Dcorner

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect member names for Point.

Naming the second Point member incorrectly.

The Point struct has members 'x' and 'y'. The Rectangle has a second Point named 'bottomRight'.

Practice

1. What is a nested structure in C programming?

easy

A. A structure that contains another structure as a member

B. A structure with only one member

C. A structure declared inside a function

D. A structure that uses pointers only

Solution

1. Step 1: Understand structure composition

   A nested structure means one structure is included inside another as a member.

2. Step 2: Rule out distractors

   The other options describe unrelated concepts: a structure using pointers only, with only one member, or declared inside a function.

3. Final Answer:

   A structure that contains another structure as a member -> Option A

4. Quick Check:

   Nested structure = structure inside structure [OK]

Hint: Nested means one structure inside another [OK]

Common Mistakes:

• Thinking nested means pointer usage
• Confusing nested with single-member structures
• Assuming nested means declared inside functions

2. Which of the following is the correct syntax to access a member of a nested structure in C?

easy

A. outer.inner->member

B. outer->inner->member

C. outer.inner.member

D. outer->inner.member

Solution

1. Step 1: Identify access operator for nested structures

   When using nested structures (not pointers), use dot notation for each level: outer.inner.member.

2. Step 2: Understand pointer vs non-pointer access

   Arrow (->) is used only when accessing members through pointers, which is not stated here.

3. Final Answer:

   outer.inner.member -> Option C

4. Quick Check:

   Use dot for nested struct members [OK]

Hint: Use dot notation for nested struct members [OK]

Common Mistakes:

• Using arrow (->) when not using pointers
• Mixing dot and arrow incorrectly
• Confusing member access syntax

3. What is the output of the following C code?

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

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

int main() {
    Person p = {"Alice", {15, 8, 1990}};
    printf("%d-%d-%d", p.birthday.day, p.birthday.month, p.birthday.year);
    return 0;
}

medium

A. 15-8-1990

B. Alice-15-8

C. 1990-8-15

D. Compilation error

Solution

1. Step 1: Understand structure initialization

   Person p is initialized with name "Alice" and birthday as Date {15, 8, 1990}.

2. Step 2: Trace printf output

   printf prints p.birthday.day (15), p.birthday.month (8), p.birthday.year (1990) separated by dashes.

3. Final Answer:

   15-8-1990 -> Option A

4. Quick Check:

   Print nested struct members correctly [OK]

Hint: Access nested members with dot notation [OK]

Common Mistakes:

• Printing name instead of date
• Mixing order of day, month, year
• Forgetting to initialize nested struct

4. Identify the error in this nested structure code snippet:

struct Address {
    char city[20];
    int zip;
};

struct Employee {
    char name[30];
    struct Address addr;
};

int main() {
    struct Employee emp;
    emp.addr->zip = 12345;
    return 0;
}

medium

A. Missing semicolon after struct definitions

B. Using '->' operator on a non-pointer structure variable

C. Incorrect declaration of nested structure

D. Cannot assign integer to zip member

Solution

1. Step 1: Check member access syntax

   emp.addr is a structure variable, not a pointer, so '->' operator is invalid here.

2. Step 2: Correct operator usage

   Use dot operator '.' to access zip: emp.addr.zip = 12345;

3. Final Answer:

   Using '->' operator on a non-pointer structure variable -> Option B

4. Quick Check:

   Use '.' for struct variables, '->' for pointers [OK]

Hint: Use '.' for struct, '->' only for pointers [OK]

Common Mistakes:

• Using '->' on struct variables
• Confusing pointer and non-pointer access
• Ignoring compiler error messages

5. Given the following nested structures, how would you write a function in C that takes a Person and returns the birth year?

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

typedef struct {
    char name[50];
    Date birthday;
} Person;

// Function prototype here

Which of the following is the correct function definition?

hard

A. int getBirthYear(Person *p) { return p.birthday->year; }

B. int getBirthYear(Person *p) { return p->birthday.year; }

C. int getBirthYear(Person p) { return p.year; }

D. int getBirthYear(Person p) { return p.birthday.year; }

Solution

1. Step 1: Understand parameter passing

   The function takes a Person by value, so use dot notation to access members.

2. Step 2: Access nested member correctly

   Access birthday.year as p.birthday.year since p is not a pointer.

3. Final Answer:

   int getBirthYear(Person p) { return p.birthday.year; } -> Option D

4. Quick Check:

   Use dot for struct value parameters [OK]

Hint: Use dot for struct, arrow for pointer parameters [OK]

Common Mistakes:

• Using arrow (->) on non-pointer parameter
• Accessing wrong member name
• Confusing pointer and value parameter syntax