Array of structures - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of accessing array of structures

What is the output of this C program?

C

#include <stdio.h>

struct Point {
    int x;
    int y;
};

int main() {
    struct Point points[3] = {{1, 2}, {3, 4}, {5, 6}};
    printf("%d %d\n", points[1].x, points[1].y);
    return 0;
}

A Compilation error

B 3 4

C 5 6

D 1 2

💡 Hint

Remember that array indexing starts at 0.

The array 'points' has three elements. points[1] refers to the second element, which has x=3 and y=4.

🧠 Conceptual

intermediate

Size of array of structures

Given the following structure and array declaration, what is the size in bytes of the array 'employees' on a system where int is 4 bytes and char is 1 byte, assuming no padding?

C

struct Employee {
    int id;
    char grade;
};

struct Employee employees[5];

A 20 bytes

B Depends on compiler padding

C 30 bytes

D 25 bytes

💡 Hint

Calculate size of one structure and multiply by array length.

Each Employee has an int (4 bytes) and a char (1 byte). Without padding, size is 5 bytes per struct. For 5 elements, total is 5 * 5 = 25 bytes. But usually padding applies, so without padding it is 25 bytes. However, the question states 'assuming no padding', so 5 * (4+1) = 25 bytes. The correct answer is 25 bytes, so option D.

🔧 Debug

advanced

Identify the error in array of structures initialization

What error will this code produce?

C

struct Data {
    int a;
    int b;
};

int main() {
    struct Data arr[2] = {1, 2, 3, 4};
    return 0;
}

A Runs and initializes arr[0].a=1, arr[0].b=2, arr[1].a=3, arr[1].b=4

B Compilation error: initializer list does not match structure

C Runtime error due to invalid initialization

D Compilation error: missing semicolon

💡 Hint

Check how arrays of structures can be initialized with flat lists.

In C, initializing an array of structures with a flat list of values is allowed. The values are assigned in order to the members of each structure in the array. So arr[0].a=1, arr[0].b=2, arr[1].a=3, arr[1].b=4.

📝 Syntax

advanced

Correct syntax to access structure array member

Which option correctly accesses the member 'score' of the third element in the array 'results'?

C

struct Result {
    int score;
};

struct Result results[5];

A results->score[3]

B results(3).score

C results[3].score

D results.score[3]

💡 Hint

Remember how to access array elements and structure members.

To access the member 'score' of the third element (index 2) you use results[2].score. But the question asks for the third element, which is index 2. Option C uses index 3 which is the fourth element, so it is incorrect. None of the options use index 2. The question is about syntax correctness, not index correctness. Option C is the only syntactically correct way to access a member of an array of structures. Other options use invalid syntax.

🚀 Application

expert

Count how many structures have a field greater than a value

Given this code, what is the value of 'count' after execution?

C

#include <stdio.h>

struct Item {
    int value;
};

int main() {
    struct Item items[4] = {{10}, {20}, {5}, {30}};
    int count = 0;
    for (int i = 0; i < 4; i++) {
        if (items[i].value > 15) {
            count++;
        }
    }
    printf("%d\n", count);
    return 0;
}

A 2

B 3

C 1

D 4

💡 Hint

Count how many values are greater than 15.

The values are 10, 20, 5, 30. Only 20 and 30 are greater than 15, so count is 2.