double assignment in c

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Doubly Linked List in C

A doubly linked list is a type of linked list in which each node contains 3 parts, a data part and two addresses, one points to the previous node and one for the next node. It differs from the singly linked list as it has an extra pointer called previous that points to the previous node, allowing the traversal in both forward and backward directions.

In this article, we will learn about the doubly linked list implementation in C. We will also look at the working of the doubly linked list and the basic operations that can be performed using the doubly linked list in C.

Doubly Linked List Representation in C

A doubly linked list is represented in C as the pointer to the head (i.e. first node) in the list. Each node in a doubly linked list contains three components:

Data: data is the actual information stored in the node.
Next: next is a pointer that links to the next node in the list.
Prev: previous is a pointer that links to the previous node in the list.

Implementation of Doubly Linked List in C

To implement a doubly linked list in C first, we need to define a node that has three parts: data, a pointer to the next node, and a pointer to the previous node, and then create a new node.

We can create a node using the structure which allows us to combine different data types into single type.

Define a Node in Doubly Linked List

To define a structure of a node in doubly linked list use the below format:

We can then dynamically create the node using malloc() and assign the values to the next, prev and data fields. It is generally preferred to create a function that creates a node, assign the data field and return the pointer to that node.

Basic Operations on C Doubly Linked List

We can perform the following basic operations in a doubly-linked list:

1. Insertion in Doubly Linked List in C

Inserting a new node in a doubly linked list can be done in a similar way like inserting a new node in a singly linked list but we have to maintain the link of previous node also. We have three scenarios while inserting a node in a doubly linked list:

Insertion at the beginning of the list.
Insertion at the end of the list.
Insertion in the middle of the list.

a. Insertion at the Beginning of the Doubly Linked List

To insert a new node at the beginning of the doubly linked list follow the below approach:

Create a newNode with data field assigned the given value. If the list is empty: Set newNode->next to NULL. Set newNode->prev to NULL. Update the head pointer to point to newNode. If the list is not empty: Set newNode->next to head. Set newNode->prev to NULL. Set head->prev to newNode. Update the head pointer to point to newNode.

Time Complexity: O(1), as insertion is done at front so we are not traversing through the list. Space Complexity: O(1)

b. Insertion at the End of the Doubly Linked List

To insert a new node at the end of the doubly linked list, follow the below approach:

Create a newNode with data field assigned the given value. If the list is empty: Set newNode->next to NULL. Set newNode->prev to NULL. Update the head pointer to point to newNode. If the list is not empty: Traverse the list to find the last node (where last->next == NULL). Set last->next to newNode. Set newNode->prev to last. Set newNode->next to NULL.

Time Complexity : O(n), as insertion is done at the end, so we need to traverse through the list. Space Complexty: O(1)

c. Insertion in the Middle of the Doubly Linked List

For inserting a node at a specific position in a doubly linked list follow the below approach:

Create a newNode. Find the size of the list to ensure the position is within valid bounds. If the position is 0 (or 1 depending on your indexing): Use the insertion at the beginning approach. If the position is equal to the size of the list: Use the insertion at the end approach. If the position is valid and not at the boundaries: Traverse the list to find the node immediately before the desired insertion point (prevNode). Set newNode->next to prevNode->next. Set newNode->prev to prevNode. If prevNode->next is not NULL, set prevNode->next->prev to newNode. Set prevNode->next to newNode.

Time Complexity : O(n), as insertion is done in between, so we need to traverse through the list until we reach the desired position. Space Complexity: O(1)

2. Deletion in a Doubly Linked List in C

Just like insertion, we have three scenarios while deleting a node in a doubly linked list:

Deletion from the beginning of the list.
Deletion from the end of the list.
Deletion at specific position of the list.

a. Deletion at the Beginning of the Doubly Linked List

To delete a node at the beginning of the doubly linked list, follow the below approach:

Check if the List is Empty : If true, there's nothing to delete. Check if the List Contains Only One Node : Set head to NULL. Free the memory of the node. If the List Contains More Than One Node : Update head to head->next. Set the prev of the new head to NULL. Free the memory of the old head.

Time Complexity : O(1), as deletion is done at front so we are not traversing through the list.

b. Deletion at the End of the Doubly Linked List

To delete a node at the end of the doubly linked list, follow the below approach:

Check if the List is Empty: If true, there's nothing to delete. If the List is Not Empty: Traverse to the last node using a loop. Check if the last node is the only node (head->next == NULL): Update head to NULL. If more than one node: Set the next of the second last node (last->prev) to NULL. Free the memory of the last node.

Time Complexity : O(n), as deletion is done at the end, so we need to traverse through the list. If a tail pointer is maintained, this operation can be optimized to O(1) by directly accessing the last node.

c. Deletion at a Specific Position in Doubly Linked List

For deleting a node at a specific position in a doubly linked list, follow the below approach:

Check Position Validity : If position is 0 (or 1 depending on indexing), use deletion at the beginning. If position is the size of the list, use deletion at the end. Otherwise, proceed with the middle deletion. Traverse to the Specified Position : Use a loop to reach the node (delNode) at the desired position. If delNode is the first node, adjust head. If not, adjust delNode->prev->next and delNode->next->prev if delNode->next is not NULL. Free the Memory : Release the node to be deleted.

Time Complexity : O(n), as deletion is done in between, as we may need to traverse up to n elements to find the correct position.

3. Traversal in a Doubly Linked List in C

Traversal in a doubly linked list means visiting each node of the doubly linked list to perform some kind of operation like displaying the data stored in that node. Unlike singly linked list we can traverse in doubly linked list in both the directions.

Forward Traversal: From head node to tail node
Reverse Traversal: From tail node to head node

a. Forward Traversal in Doubly Linked List

For traversing in a forward direction in a doubly linked list, follow the below approach:

Create a temporary pointer ptr and copy the head pointer into it. Traverse through the list using a while loop. Keep moving the value of temp pointer variable ptr to ptr->next until the last node whose next part contains null is found. During each iteration of the loop, perform the desired operation.

Time Complexity : O(n), as we need to traverse through the whole list containing n number of nodes.

b. Reverse Traversal in Doubly Linked List

For traversing in a reverse direction in a doubly linked list, follow the below approach:

Create a temporary pointer ptr and copy the tail pointer into it. Traverse through the list using a while loop. Keep moving the value of temp pointer variable ptr to ptr->prev until the first node whose prev part contains null is found. During each iteration of the loop, perform the desired operation .

Time Complexity : O(n), as here also we need to traverse through the whole list containing n number of nodes.

C Program to Implement Doubly Linked List

The below program demonstrates all the major operations of a doubly linked list: insertion (at the beginning, at the end, and at a specific position), deletion (at the beginning, at the end, and at a specific position), and traversal (forward and reverse).

Advantages of Doubly Linked List

Unlike singly linked list, we can traverse in both the direction forward and reverse using doubly linked list which makes operations like reversing and searching from end easier and more efiicient.
It is fast and easier to delete a node in doubly linked list, if the node to be deleted is given then we can search the previous node quickly and update it's links.
Inserting a new node is also easier in doubly linked list, as we can simply insert a new node before a given node by updating the links.
In a doubly linked list, we need not to keep track of the previous node during traversal that is very useful in data structures like the binary tree where we need to keep track of the parent node.

Disadvantages of Doubly Linked List

Although doubly linked lists provide more flexibility and efficiency in certain operations compared to singly linked lists, they also consume more memory as they need to store an extra pointer for each node.
The insertion and deletion code in a doubly linked list is more complex as we need to maintain the previous links too.
For insertion and deletion at a specific position in a doubly linked list we need to traverse from a head node to the specified node that can be time-consuming in case of larger lists.
For each node we have to maintain two pointers in a doubly linked list that leads to the overhead of maintaining and updating these pointers during insertions and deletions.

Frequently Asked Questions on Doubly Linked List

What is a doubly linked list (dll).

A doubly linked list is a type of linked list in which each node contains a pointer to the next node as well as the previous node in the sequence.

How is a Doubly Linked List Represented in C?

In C, a doubly linked list node can be represented as a structure that contains an integer data field and two pointers, next and prev, that points to the next and previous nodes respectively.The nodes at the ends (i.e., those that do not have a previous or next node)are set as NULL.

What are the Basic Operations that can be Performed on a Doubly Linked List in C?

The basic operations that can be performed on a DLL in C are insertion at the head, deletion at the head, insertion at the tail, deletion at the tail, insertion and deletion at a specific position and traversal in both forward and backward directions.

What are the Advantages of a Doubly Linked List over a Singly Linked List?

The main advantage of a doubly linked list over a singly linked list is that it can be traversed in both forward and backward directions. The delete operation in DLL is more efficient if a pointer to the node to be deleted is given. We can quickly insert a new node before a given node.

What are the Applications of Doubly Linked List?

The doubly linked list can be used in various applications such as web browsers for backward and forward navigation of web pages, LRU (Least Recently Used) / MRU (Most Recently Used) Cache, maintaining undo and redo functionalities, and in Operating Systems to keep track of processes that are being executed at that time.

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C Functions

C structures, c reference, c declare multiple variables, declare multiple variables.

To declare more than one variable of the same type, use a comma-separated list:

You can also assign the same value to multiple variables of the same type:

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C Type Conversion

In C programming, we can convert the value of one data type ( int, float , double , etc.) to another. This process is known as type conversion . Let's see an example,

Here, we are assigning the double value 34.78 to the integer variable number. In this case, the double value is automatically converted to integer value 34 .

This type of conversion is known as implicit type conversion . In C, there are two types of type conversion:

Implicit Conversion
Explicit Conversion
Implicit Type Conversion In C

As mentioned earlier, in implicit type conversion, the value of one type is automatically converted to the value of another type. For example,

The above example has a double variable with a value 4150.12 . Notice that we have assigned the double value to an integer variable.

Here, the C compiler automatically converts the double value 4150.12 to integer value 4150 .

Since the conversion is happening automatically, this type of conversion is called implicit type conversion.

Example: Implicit Type Conversion

The code above has created a character variable alphabet with the value 'a' . Notice that we are assigning alphabet to an integer variable.

Here, the C compiler automatically converts the character 'a' to integer 97 . This is because, in C programming, characters are internally stored as integer values known as ASCII Values .

ASCII defines a set of characters for encoding text in computers. In ASCII code, the character 'a' has integer value 97 , that's why the character 'a' is automatically converted to integer 97 .

If you want to learn more about finding ASCII values, visit find ASCII value of characters in C .

Explicit Type Conversion In C

In explicit type conversion, we manually convert values of one data type to another type. For example,

We have created an integer variable named number with the value 35 in the above program. Notice the code,

(double) - represents the data type to which number is to be converted
number - value that is to be converted to double type
Example: Explicit Type Conversion

We have created a variable number with the value 97 in the code above. Notice that we are converting this integer to character.

(char) - explicitly converts number into character
number - value that is to be converted to char type
Data Loss In Type Conversion

In our earlier examples, when we converted a double type value to an integer type, the data after decimal was lost.

Here, the data 4150.12 is converted to 4150 . In this conversion, data after the decimal, .12 is lost.

This is because double is a larger data type ( 8 bytes ) than int ( 4 bytes ), and when we convert data from larger type to smaller, there will be data loss..

Similarly, there is a hierarchy of data types in C programming. Based on the hierarchy, if a higher data type is converted to lower type, data is lost, and if lower data type is converted to higher type, no data is lost.

Data is lost when converting from a higher data type to a lower data type

data loss - if long double type is converted to double type
no data loss - if char is converted to int

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Assignment Operators in C

In C language, the assignment operator stores a certain value in an already declared variable. A variable in C can be assigned the value in the form of a literal, another variable, or an expression.

The value to be assigned forms the right-hand operand, whereas the variable to be assigned should be the operand to the left of the " = " symbol, which is defined as a simple assignment operator in C.

In addition, C has several augmented assignment operators.

The following table lists the assignment operators supported by the C language −

Simple Assignment Operator (=)

The = operator is one of the most frequently used operators in C. As per the ANSI C standard, all the variables must be declared in the beginning. Variable declaration after the first processing statement is not allowed.

You can declare a variable to be assigned a value later in the code, or you can initialize it at the time of declaration.

You can use a literal, another variable, or an expression in the assignment statement.

Once a variable of a certain type is declared, it cannot be assigned a value of any other type. In such a case the C compiler reports a type mismatch error.

In C, the expressions that refer to a memory location are called "lvalue" expressions. A lvalue may appear as either the left-hand or right-hand side of an assignment.

On the other hand, the term rvalue refers to a data value that is stored at some address in memory. A rvalue is an expression that cannot have a value assigned to it which means an rvalue may appear on the right-hand side but not on the left-hand side of an assignment.

Variables are lvalues and so they may appear on the left-hand side of an assignment. Numeric literals are rvalues and so they may not be assigned and cannot appear on the left-hand side. Take a look at the following valid and invalid statements −

Augmented Assignment Operators

In addition to the = operator, C allows you to combine arithmetic and bitwise operators with the = symbol to form augmented or compound assignment operator. The augmented operators offer a convenient shortcut for combining arithmetic or bitwise operation with assignment.

For example, the expression "a += b" has the same effect of performing "a + b" first and then assigning the result back to the variable "a".

Run the code and check its output −

Similarly, the expression "a <<= b" has the same effect of performing "a << b" first and then assigning the result back to the variable "a".

Here is a C program that demonstrates the use of assignment operators in C −

When you compile and execute the above program, it will produce the following result −

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c - Multiple assignment in one line - Stack Overflow
To be bug free, and to have (b + i)->foo equal to a, the one-line assignment must be splitted in two assignments: a = reallocB(); (b + i)->foo = a;
Assignment Operators in C - GeeksforGeeks
Different types of assignment operators are shown below: 1. “=”: This is the simplest assignment operator. This operator is used to assign the value on the right to the variable on the left. Example: 2. “+=”: This operator is combination of ‘+’ and ‘=’ operators.
Doubly Linked List in C - GeeksforGeeks
C Program to Implement Doubly Linked List. The below program demonstrates all the major operations of a doubly linked list: insertion (at the beginning, at the end, and at a specific position), deletion (at the beginning, at the end, and at a specific position), and traversal (forward and reverse). C
C Declare Multiple Variables - W3Schools
To declare more than one variable of the same type, use a comma-separated list: You can also assign the same value to multiple variables of the same type: Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, PHP, Python, Bootstrap, Java and XML.
What is the difference/ advantage of doing double assignment?
Now, what you do sometimes see is the assignment of two (or more) variables to some value at the same time, like this: In this case, you're assigning 5 to y, and then assigning the value of that expression (again, 5) to x. This ensures that both x and y get the same value.
C Type Conversion (With Examples) - Programiz
In C programming, we can convert the value of one data type (int, float, double, etc.) to another. This process is known as type conversion. Let's see an example, return 0; // Output: 34. Here, we are assigning the double value 34.78 to the integer variable number. In this case, the double value is automatically converted to integer value 34.
How can I declare and define multiple variables in one line ...
As others have mentioned, from C++17 onwards you can make use of structured bindings for multiple variable assignments. Combining this with std::array and template argument deduction we can write a function that assigns a value to an arbitrary number of variables without repeating the type or value.
C Programming: Assignment Operators with Examples - w3resource
In C programming, assignment operators are used to assign values to variables. The simple assignment operator is =. C also supports shorthand assignment operators that combine an operation with assignment, making the code more concise. =: Simple assignment, assigns a value to a variable.
Assignment Operators in C - Online Tutorials Library">Assignment Operators in C - Online Tutorials Library
Assignment Operators in C - In C language, the assignment operator stores a certain value in an already declared variable. A variable in C can be assigned the value in the form of a literal, another variable, or an expression.
Assignment - C++ Forum - C++ Users">Multiple Assignment - C++ Forum - C++ Users
I know that c++ allows for statements like int a, b, c; a = b = c = 10; but is there a way that I can turn a += 5; b += 5; c += 5; into one line? Such as a,b,c += 5; Thanks!