Array traversal in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of array traversal with pointer arithmetic

What is the output of the following C++ code?

C++

#include <iostream>
int main() {
    int arr[] = {10, 20, 30, 40, 50};
    int *p = arr;
    for (int i = 0; i < 5; ++i) {
        std::cout << *(p + i) << " ";
    }
    return 0;
}

A 50 40 30 20 10

B 10 20 30 40 50

C 10 20 30 40

D Compilation error

💡 Hint

Pointer arithmetic moves through the array elements in order.

The pointer p points to the first element of the array. Adding i moves the pointer to the next elements. Dereferencing *(p + i) prints each element in order.

❓ Predict Output

intermediate

Output of array traversal with range-based for loop

What will this C++ program print?

C++

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

A 0 2 4 6 8

B 1 2 3 4 5

C 2 4 6 8 10

D Compilation error

💡 Hint

The loop multiplies each element by 2 before printing.

The range-based for loop goes through each element in arr. Each element is multiplied by 2 and printed with a space.

❓ Predict Output

advanced

Output of nested array traversal

What is the output of this nested loop traversing a 2D array?

C++

#include <iostream>
int main() {
    int matrix[2][3] = {{1, 2, 3}, {4, 5, 6}};
    for (int i = 0; i < 2; ++i) {
        for (int j = 0; j < 3; ++j) {
            std::cout << matrix[i][j] << " ";
        }
    }
    return 0;
}

A 1 2 3 4 5 6

B Compilation error

C 1 4 2 5 3 6

D 1 2 3 1 2 3

💡 Hint

The outer loop goes through rows, inner loop through columns.

The code prints all elements row by row: first row elements then second row elements.

❓ Predict Output

advanced

Output of array traversal with incorrect loop condition

What happens when this code runs?

C++

#include <iostream>
int main() {
    int arr[] = {5, 10, 15};
    for (int i = 0; i <= 3; ++i) {
        std::cout << arr[i] << " ";
    }
    return 0;
}

A 5 10 15 garbage_value or runtime error

B 5 10 15 0

C Compilation error

D 5 10 15

💡 Hint

The loop goes one step beyond the array size.

The loop accesses arr[3], which is out of bounds. This causes undefined behavior: it may print garbage or cause a runtime error.

🧠 Conceptual

expert

Identifying the number of elements traversed

Given the code below, how many elements will be printed?

C++

#include <iostream>
int main() {
    int arr[4] = {7, 14, 21, 28};
    int *ptr = arr + 1;
    for (int i = 0; i < 3; ++i) {
        std::cout << *(ptr + i) << " ";
    }
    return 0;
}

A 4

B 2

C 1

D 3

💡 Hint

Pointer starts at second element, loop runs 3 times.

Pointer ptr points to arr[1]. Loop runs 3 times printing arr[1], arr[2], arr[3]. So 3 elements printed.