Arrays and Strings : MCQs & PYQs with Explanation

Option A

In C++, is_array<T>::value is a type trait provided in the <type_traits> header. Its purpose is only to determine whether the given type T is an array type or not.

• If T is an array (like int arr[10] or char name[]), then is_array<T>::value becomes true.
• If T is not an array (like int, float*, string, class objects, etc.), then it becomes false.

It does NOT check whether an array is 1D or multi-dimensional. It only checks “Is this type an array?”

Option C

An array in C++ is a collection of similar type (homogeneous) items a single variable, stored in unique and successive (contiguous) memory location. An array items are accessed by index (starting from 0). To declare an array, specify the data type, array name, and size inside square brackets [].

• The statement int array[10]; is correct. This declares an array of 10 integers.

Option B

In most programming languages, arrays are zero-indexed, meaning the first element is at index 0, the second at index 1, and so on. Therefore, to access the nth element of an array, you need to use array[n-1].

Option C

In C++, you cannot directly add C-style character arrays using the + operator. In the given code, s1 and s2 are character arrays, and the statement char s3[12] = s1 + " " + s2; is invalid. C++ does not allow concatenation of arrays or char* using +.

Option C

In C++, the rank() function (std::rank<T>() from <type_traits>) is used with arrays to determine the number of dimensions of the array, not the size of each dimension or the total number of elements. For example, a one-dimensional array has a rank of 1, a two-dimensional array has a rank of 2, and so on.
This is useful when working with multidimensional arrays to programmatically determine their structure.

#include <iostream>
#include <type_traits>
using namespace std;
int main()
{
    int arr1[6];        
    int arr2[2][3];     
    int arr3[2][3][4];
    cout << "Rank (Dimension) of arr1: " << std::rank<decltype(arr1)>::value << endl;
    cout << "Rank (Dimension) of arr2: " << std::rank<decltype(arr2)>::value << endl;
    cout << "Rank (Dimension) of arr3: " << std::rank<decltype(arr3)>::value << endl;
    return 0;
}
OUTPUT
Rank (Dimension) of arr1: 1
Rank (Dimension) of arr2: 2
Rank (Dimension) of arr3: 3

• The decltype(arr1) gets the type of the array (int[6]).
• The std::rank<type>::value returns the number of dimensions of the array.