[Data structure] Linked list: When defining the storage structure of the linked list, why is the pointer to the first address of the next data a structure type? &&Summary: Implement linked list node deletion operation in C and C++:

Example of linked storage structure – linked list

#include <iostream>

struct Node {<!-- -->
    int data;
    Node* next;
};

int main() {<!-- -->
    //Example of linked storage structure - linked list
    Node* head = nullptr;
    Node* newNode;

    // Create linked list
    for (int i = 1; i <= 5; i + + ) {<!-- -->
        newNode = new Node;
        newNode->data = i;
        newNode->next = head;
        head = newNode;
    }

    // Traverse the linked list
    std::cout << "Linked list elements: ";
    Node* current = head;
    while (current != nullptr) {<!-- -->
        std::cout << current->data << " ";
        current = current->next;
    }
    std::cout << std::endl;

    // release memory
    current = head;
    while (current != nullptr) {<!-- -->
        Node* temp = current;
        current = current->next;
        delete temp;
    }

    return 0;
}

In this example, we use a linked list as a linked storage structure to store data elements. The logical structure of a linked list is a linear structure, but the data elements are connected to each other through pointers and there is no fixed physical order. This makes the linked list more flexible and elements can be inserted and deleted dynamically.

Why is the pointer to the first address of the next data of type Node?

In the node structure of a linked list, the pointer to the next data element is usually a node pointer of the same type, that is, Node* type.
This is because each node of the linked list is essentially an independent data structure, which contains the data itself and a pointer to the next node.

Consider the following reasons:

Consistency: Defining the pointer to the next node to be of the same type as the node provides consistency. This means that each node contains the same type of data and the same type of pointer. In this way, the code when operating the linked list is more consistent and simpler.
Recursion: A linked list is a recursive data structure in which each node is itself a linked list. Therefore, if we define the pointer to the next node as a different type, it may result in more complex code and type conversions.
Easy to understand and maintain: Using pointers of the same type makes the code easier to understand and maintain. Developers can more easily identify relationships between nodes.

In C++, using custom structures or classes to define node types is a common and effective way, but in actual development, templates and other methods can also be used to improve flexibility. However, using a pointer of type Node* is usually the most common and simple approach.

Is this related to pointers or functions?
Yes, this has to do with pointers and functions, since the node structure of a linked list usually includes a pointer to the next node, and the type of this pointer is usually the same as the type of the node structure itself.

Pointer type: In a linked list, the connection between nodes is achieved through pointers. Node* next in the node structure represents a pointer pointing to the next node. The type of this pointer is Node* because it points to another node, the next node, which is also of type Node.
Function operations: Operations such as creation, insertion, deletion and traversal of linked lists usually involve processing pointers and performing operations related to linked list nodes. These operations are typically implemented using functions whose parameters and return types often involve node types and pointers.

Therefore, the type of node structure and pointer type are related to the relationship between linked list operations and nodes. This design makes linked list operations more consistent and understandable. The node structure definition of a linked list usually involves two main elements: data (such as int data) and a pointer to the next node (such as Node* next), which work together Work to build the logical and storage structure of the linked list.

– What are the type requirements for different parameters in function operations?

**//This part contains comparisons between C language and C++

C language implementation:

In linked list operations, the type requirements of different parameters of functions usually vary according to the specific operations performed. Here are some common linked list operations and their parameter type requirements:

Create a new node: Usually, creating a new linked list node requires specifying the data stored in the node, usually an integer or a custom data type. Functions that create new nodes may accept data as arguments.
```
Node* createNode(int data);
```
Insert node: Inserting a node usually requires specifying the location to be inserted and the data of the node. Parameters usually include the location to insert (usually a pointer to a node) and the data to insert.
```
void insertNode(Node* position, int data);
```
Delete Node: Deleting a node usually requires specifying the node to be deleted. The argument is usually a pointer to the node to be deleted.
```
void deleteNode(Node* nodeToDelete);
```
Traversing a linked list: When traversing a linked list, you usually need to provide a pointer to the head of the linked list. The parameter is usually a pointer to the head of the linked list, and then a loop or recursion is used to access all nodes in the linked list.
```
void traverseLinkedList(Node* head);
```

These are some common linked list operations, each of which has different requirements for parameter types. Generally speaking, functions require parameter types that match the node structure of the linked list in order to perform the corresponding operation efficiently. The correct matching of parameter types is crucial to ensure the correctness and safety of linked list operations. In addition, functions can also return a value, usually a node pointer or other information about the linked list operation.

C++ Implementation

Let’s use C++ to implement a few common linked list operations and show the requirements for different parameter types:

#include <iostream>

//Define the linked list node structure
struct Node {<!-- -->
    int data;
    Node* next;
};

// The function that creates a new node requires data as a parameter
Node* createNode(int data) {<!-- -->
    Node* newNode = new Node;
    newNode->data = data;
    newNode->next = nullptr;
    return newNode;
}

// The function to insert nodes requires the insertion position and data as parameters
void insertNode(Node* & amp;position, int data) {<!-- -->
    if (position == nullptr) {<!-- -->
        std::cout << "Error: Invalid position." << std::endl;
        return;
    }

    Node* newNode = createNode(data);
    newNode->next = position->next;
    position->next = newNode;
}

// The function to delete nodes requires the node to be deleted as a parameter
void deleteNode(Node* & amp;nodeToDelete) {<!-- -->
    if (nodeToDelete == nullptr) {<!-- -->
        std::cout << "Error: Invalid node to delete." << std::endl;
        return;
    }

    Node* temp = nodeToDelete;
    nodeToDelete = nodeToDelete->next;
    delete temp;
}

// The function that traverses the linked list requires the head of the linked list as a parameter
void traverseLinkedList(Node* head) {<!-- -->
    Node* current = head;
    while (current != nullptr) {<!-- -->
        std::cout << current->data << " ";
        current = current->next;
    }
    std::cout << std::endl;
}

int main() {<!-- -->
    // Create linked list header
    Node* head = createNode(1);

    //Insert node
    insertNode(head, 2);
    insertNode(head->next, 3);

    // Traverse the linked list
    std::cout << "Linked list elements: ";
    traverseLinkedList(head);

    // delete node
    deleteNode(head->next);

    // Traverse the linked list
    std::cout << "Linked list elements after deletion: ";
    traverseLinkedList(head);

    // release memory
    delete head;

    return 0;
}

In the above example, we defined several functions for linked list operations:

createNode creates a new node, requiring data as parameters.
insertNode inserts a node, requiring insertion position and data as parameters.
deleteNode deletes a node and requires the node to be deleted as a parameter.
traverseLinkedList traverses the linked list and requires the head of the linked list as a parameter.

Each function has specific requirements for parameter types and performs corresponding linked list operations. This example shows how to implement these linked list operations using C++.

Comparison: It is not difficult to observe that when deleting a node, the C language is void deleteNode(Node nodeToDelete) and C++ is void
deleteNode(Node & amp;nodeToDelete)
What are the functional similarities and differences between the two? What is the function of & amp;? **

In C and C++, different ways of declaring function parameters affect how the function operates on the parameters. Specifically, the & notation is used in C++ as part of a parameter declaration, which represents passing parameters by reference. This will have some important effects on the behavior of the function, which is different from the way C language passes values.

Parameter passing (passing by value) in C language

In the C language, function parameters are passed by value, which means that the function receives a copy of the parameter, not the original data. When you modify the value of a parameter inside a function, the original data is not affected.

void deleteNode(Node* nodeToDelete) {<!-- -->
    // Modifying nodeToDelete within the function will not affect the original data
    nodeToDelete = nullptr;
}

Parameter passing (passing by reference) in C++

In C++, if you use the & notation to declare a function parameter, it means passing the parameter by reference, which means that the function receives a reference to the original data, not a copy. This allows modifications to parameters inside the function to affect the original data.

void deleteNode(Node* & amp;nodeToDelete) {<!-- -->
    // Modifying nodeToDelete within the function will affect the original data
    nodeToDelete = nullptr;
}

So, the main difference is that when passing by reference, modifications inside the function affect the original data. This is very useful in linked list operations, as you can set the original node pointer to nullptr when deleting a node, ensuring that the linked list is linked correctly. In C, you need to return the new pointer of the deleted node so that it can be updated in the original data.

In short, passing by reference in C++ allows you to modify the original data more conveniently without returning a value or manipulating a pointer to a pointer. This makes the code clearer and easier to understand, especially in operations on data structures such as linked lists.

– So, if we want to use C language to implement the function of deleting nodes and modify the original data, how should we implement it?

If you want to implement the function of deleting a node in C language and require modification of the original data, you can do this by passing a pointer to a pointer (double pointer). This allows you to modify the value of the raw pointer inside the function. Here is an example:

#include <stdio.h>
#include <stdlib.h>

//Define the linked list node structure
struct Node {<!-- -->
    int data;
    struct Node* next;
};

// Function to delete node, use pointer to pointer
void deleteNode(struct Node** head, int targetData) {<!-- -->
    struct Node* current = *head;
    struct Node* prev = NULL;

    while (current != NULL) {<!-- -->
        if (current->data == targetData) {<!-- -->
            if (prev == NULL) {<!-- -->
                // If the node to be deleted is the head node
                *head = current->next;
            } else {<!-- -->
                prev->next = current->next;
            }
            free(current);
            return;
        }
        prev = current;
        current = current->next;
    }
}

// Function to traverse the linked list
void traverseLinkedList(struct Node* head) {<!-- -->
    struct Node* current = head;
    while (current != NULL) {<!-- -->
        printf("%d ", current->data);
        current = current->next;
    }
    printf("\\
");
}

int main() {<!-- -->
    // Create linked list header
    struct Node* head = (struct Node*)malloc(sizeof(struct Node));
    head->data = 1;

    //Insert node
    head->next = (struct Node*)malloc(sizeof(struct Node));
    head->next->data = 2;
    head->next->next = NULL;

    // Traverse the linked list
    printf("Linked list elements: ");
    traverseLinkedList(head);

    // delete node
    deleteNode( & amp;head, 2);

    // Traverse the linked list
    printf("Linked list elements after deletion: ");
    traverseLinkedList(head);

    // release memory
    free(head);
    
    return 0;
}

In this example, we use a pointer to a pointer (struct Node**) as a parameter, which allows the value of the original pointer to be modified inside the function. When deleting a node, if the node to be deleted is the head node, we need to modify the value of the head pointer, so passing a pointer to the head pointer is necessary. This approach allows the original data to be modified in C language.

Summary: Implement linked list node deletion operation in C and C++:

Using pass-by-reference in C++

In C++, passing by reference is usually used to delete linked list nodes. This means that the function accepts a reference to a node pointer, and modifications to the parameters inside the function affect the original data. The sample code is as follows:

void deleteNode(Node* & amp;nodeToDelete) {<!-- -->
    // Modifying nodeToDelete within the function will affect the original data
    nodeToDelete = nullptr;
}

This approach allows for easier modification of the original data, but it is specific to C++ and does not apply to the C language.

Using double pointers in C language

In C language, if you want to modify the original data and delete the linked list node, you usually use a double pointer, that is, a pointer to a pointer (struct Node**). The value of the original pointer can be modified inside the function by passing a pointer to the head pointer. The sample code is as follows:

void deleteNode(struct Node** head, int targetData) {<!-- -->
    struct Node* current = *head;
    struct Node* prev = NULL;

    while (current != NULL) {<!-- -->
        if (current->data == targetData) {<!-- -->
            if (prev == NULL) {<!-- -->
                // If the node to be deleted is the head node
                *head = current->next;
            } else {<!-- -->
                prev->next = current->next;
            }
            free(current);
            return;
        }
        prev = current;
        current = current->next;
    }
}

This approach is suitable for C language and allows the original data to be modified inside the function.

In short, you can choose the appropriate method to implement the deletion of linked list nodes according to the programming language used. In C++, passing by reference is a convenient way, while in C, double pointers are a general way to modify the original data.