Readme.md

Arrays

An array in C++ is a collection of elements of the same data type, stored in contiguous memory locations. The elements can be accessed by their index, which is a numerical value that corresponds to the position of the element in the array.

What does array name means?

arr is a variable of type int* (pointer to int), which holds the memory address of the first element of an array. The variable arr can be used to access the elements of the array, for example, you can use arr[i] or i[arr] to access the i-th element of the array or *(arr+i) to access the i-th element of the array. Also you can use pointer arithmetic to move through the array, for example arr + 2 will point to the third element of the array

What does &array name means?

&arr is a variable of type int (*)[5], which holds the memory address of the entire array. The variable &arr can be used to get the size of the array. However, you cannot access the elements of the array using &arr directly, instead you need to use &arr[i] to access the i-th element of the array. Also you can't use pointer arithmetic to move through the array, for example &arr + 2 will not point to the third element of the array.

The difference between arr and &arr

It is important to note that when arr is used in an expression, it is implicitly converted to a pointer to the first element of the array, which is why it has the same memory address as &arr[0]. Similarly, when &arr is used in an expression, it is implicitly converted to a pointer to the array, which is why it has the same memory address as arr. However, when you use *(arr) it will give you the value of the first element of the array, and when you use *(&arr) it will give you the entire array.

The variable arr is an array of integers with a size of 5. It is an lvalue, meaning it can be used on the left side of an assignment. &arr is a pointer to the array object, an rvalue with the value of the memory address of the array. They point to the same location in memory. To differentiate, compare *(arr) and *(&arr). The first is an lvalue of type int and the second an lvalue of type int [5].

In summary, arr and &arr are different variables with different types and behaviors, arr is a pointer to the first element of the array and &arr is a pointer to the entire array, they may have the same memory address but you can't use them in the same way.

Task for You?

Run it in your compiler for further clarification

*std::cout << (arr+1) << std::endl;

*std::cout << (&arr+1) << std::endl;

calculating size of array

There are two ways to calculate the size of an array

• Dividing the total size of the array by the size of the first element sizeof(arr)/sizeof(arr[0]). This method is widely used.
• Subtracting the memory address of the last element of the array from the memory address of the first element: *(&arr+1)-arr.

Array with pointers

Arrays with functions

When using the pointer ptr to access elements of the array, adding 1 to it does not increment the memory address by 1 byte, but rather by the size of the data type of the array (in this case, an int). So when we say ptr + 1, it's equivalent to accessing the memory location that is 1 * sizeof(int) bytes away from the original memory location of ptr.

Bonus Point

When an array is passed as a parameter to a function, a pointer to the first element of the array is created, which occupies actual memory. In the main function, the array(means array name ,i.e arr) itself does not occupy memory, but in a user-defined function, the pointer to the array does occupy memory. Therefore, the size of the array may not be correctly determined in a user-defined function by sizeof(arr)/sizeof(arr[0]) because arr is a pointer with actual memory ).

Types of Arrays

1. Fixed-size arrays
2. Dynamic arrays

Sorting Algorithms

1. Bubble Sort
2. Selection Sort
3. Insertion Sort

Searching in Array

• Linear search
• Binary search

Unusual Things

1. It is not possible to determine the size of a static array at runtime using the traditional method, however, using the concept of a constant array size, the size of a static array can be obtained during runtime. This allows for the dynamic allocation of memory for a static array, enabling its size to be determined and modified at runtime.

2. When declaring an array, it is possible to initialize specific elements of the array at that time by using the syntax of assigning a value to a specific index of the array. This allows for more flexibility in initializing arrays and can be useful in certain situation.

3. It is also possible to initialize an array in a more concise way, by omitting the = sign while providing the values to be assigned to the array. This method is called uniform initialization . This way of initializing an array is considered to be more readable and can make the code more expressive. It is important to note that this method of initialization is only supported in C++11 and later versions.

4. In the context of a symbol table, the reason why we can't do arr++.The symbol table, which is used by the compiler to keep track of variables and their types, does not contain information about the specific memory addresses of variables, but rather their types and scope.