One-dimensional arrays in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of array sum calculation

What is the output of this C++ code that sums elements of an array?

C++

#include <iostream>
int main() {
    int arr[5] = {1, 2, 3, 4, 5};
    int sum = 0;
    for(int i = 0; i < 5; i++) {
        sum += arr[i];
    }
    std::cout << sum << std::endl;
    return 0;
}

A 14

B Error: array index out of bounds

C 15

D 10

💡 Hint

Add all numbers from 1 to 5.

The loop adds all elements: 1+2+3+4+5 = 15.

❓ Predict Output

intermediate

Value of array element after modification

What is the value of arr[2] after running this code?

C++

#include <iostream>
int main() {
    int arr[4] = {10, 20, 30, 40};
    arr[2] = arr[1] + arr[3];
    std::cout << arr[2] << std::endl;
    return 0;
}

A 60

B 50

C 30

D Compilation error

💡 Hint

arr[2] is set to arr[1] + arr[3].

arr[1] is 20 and arr[3] is 40, so arr[2] becomes 60.

🔧 Debug

advanced

Identify the error in array initialization

What error does this code produce?

C++

#include <iostream>
int main() {
    int arr[3] = {1, 2, 3, 4};
    std::cout << arr[0] << std::endl;
    return 0;
}

A Runtime error: array index out of bounds

B No error, outputs 4

C Output: 1

D Compilation error: too many initializers for 'int [3]'

💡 Hint

Array size is 3 but 4 values are given.

The array is declared with size 3 but initialized with 4 values, causing a compilation error.

📝 Syntax

advanced

Correct syntax to declare and initialize an array

Which option correctly declares and initializes an array of 4 integers with values 5, 10, 15, 20?

A int arr[4] = {5, 10, 15, 20};

B int arr[4] = (5, 10, 15, 20);

C int arr[] = {5, 10, 15, 20};

D int arr = {5, 10, 15, 20};

💡 Hint

Use curly braces and specify size correctly.

Option A correctly declares an array of size 4 and initializes it with 4 values using curly braces.

🚀 Application

expert

Find the number of elements greater than 10

What is the output of this program that counts elements greater than 10 in an array?

C++

#include <iostream>
int main() {
    int arr[6] = {5, 12, 7, 18, 10, 20};
    int count = 0;
    for(int i = 0; i < 6; i++) {
        if(arr[i] > 10) {
            count++;
        }
    }
    std::cout << count << std::endl;
    return 0;
}

A 2

B 3

C 5

D 4

💡 Hint

Count how many numbers are strictly greater than 10.

The numbers greater than 10 are 12, 18, and 20, so count is 3.