用于删除链表中节点的 C++ 程序

我们在之前关于单链表的文章中讨论了链表介绍和链表插入。
让我们制定问题陈述以了解删除过程。给定一个“键”，删除链表中该键的第一次出现。

迭代方法：
要从链表中删除一个节点，我们需要执行以下步骤。
1）找到要删除的节点的前一个节点。
2）改变前一个节点的下一个。
3) 为要删除的节点释放内存。

由于链表的每个节点都是使用 C 中的 malloc() 动态分配的，因此我们需要调用 free() 来释放为要删除的节点分配的内存。

C++

// A complete working C++ program to
// demonstrate deletion in singly 
// linked list with class 
#include 
using namespace std;
  
// A linked list node
class Node{
public:
    int data;
    Node* next;
};
  
// Given a reference (pointer to pointer)
// to the head of a list and an int, 
// inserts a new node on the front of the
// list. 
void push(Node** head_ref, int new_data)
{
    Node* new_node = new Node();
    new_node->data = new_data;
    new_node->next = (*head_ref);
    (*head_ref) = new_node;
}
  
// Given a reference (pointer to pointer)
// to the head of a list and a key, deletes
// the first occurrence of key in linked list 
void deleteNode(Node** head_ref, int key)
{
      
    // Store head node
    Node* temp = *head_ref;
    Node* prev = NULL;
      
    // If head node itself holds
    // the key to be deleted
    if (temp != NULL && temp->data == key)
    {
        *head_ref = temp->next; // Changed head
        delete temp;            // free old head
        return;
    }
  
    // Else Search for the key to be deleted, 
    // keep track of the previous node as we
    // need to change 'prev->next' */
      else
    {
    while (temp != NULL && temp->data != key)
    {
        prev = temp;
        temp = temp->next;
    }
  
    // If key was not present in linked list
    if (temp == NULL)
        return;
  
    // Unlink the node from linked list
    prev->next = temp->next;
  
    // Free memory
    delete temp;
    }
}
  
// This function prints contents of
// linked list starting from the 
// given node 
void printList(Node* node)
{
    while (node != NULL) 
    {
        cout << node->data << " ";
        node = node->next;
    }
}
  
// Driver code
int main()
{
      
    // Start with the empty list 
    Node* head = NULL;
  
    // Add elements in linked list
    push(&head, 7);
    push(&head, 1);
    push(&head, 3);
    push(&head, 2);
  
    puts("Created Linked List: ");
    printList(head);
  
    deleteNode(&head, 1);
    puts("
Linked List after Deletion of 1: ");
      
    printList(head);
      
    return 0;
}
  
// This code is contributed by ac121102

输出：

Created Linked List: 
 2  3  1  7 
Linked List after Deletion of 1: 
 2  3  7

递归方法：

要递归删除链表的节点，我们需要执行以下步骤。

1.我们传递node*（节点指针）作为函数的引用（如node* &head）

2.现在由于当前节点指针是从前一个节点的下一个节点派生的（通过引用传递）所以现在如果当前节点指针的值改变了，前一个下一个节点的值也会改变，这是删除时所需的操作一个节点（即，将前一个节点的下一个指向当前节点的（包含键）下一个）。

3.找到包含给定值的节点。

4. 存储该节点以便稍后使用 free()函数释放它。

5.更改此节点指针，使其指向其下一个节点，并通过执行此前一个节点的下一个节点也得到正确链接。

下面是上述方法的实现。

C++

// C++ program to delete a node in
// singly linked list recursively
  
#include 
using namespace std;
  
struct node {
    int info;
    node* link = NULL;
    node() {}
    node(int a)
        : info(a)
    {
    }
};
  
/*
Deletes the node containing 'info' part as val and
alter the head of the linked list (recursive method)
*/
void deleteNode(node*& head, int val)
{
      
    // Check if list is empty or we 
    // reach at the end of the
    // list.
    if (head == NULL) {
        cout << "Element not present in the list
";
        return;
    }
    // If current node is the node to be deleted
    if (head->info == val) {
        node* t = head;
        head = head->link; // If it's start of the node head
                           // node points to second node
        delete (t); // Else changes previous node's link to
                    // current node's link
        return;
    }
    deleteNode(head->link, val);
}
  
// Utility function to add a 
// node in the linked list
// Here we are passing head by 
// reference thus no need to
// return it to the main function
void push(node*& head, int data)
{
    node* newNode = new node(data);
    newNode->link = head;
    head = newNode;
}
  
// Utility function to print 
// the linked list (recursive
// method)
void print(node* head)
{
      
    // cout<info << ' ';
    print(head->link);
}
  
int main()
{
    // Starting with an empty linked list
    node* head = NULL;
  
    // Adds new element at the 
    // beginning of the list
    push(head, 10);
    push(head, 12);
    push(head, 14);
    push(head, 15);
  
    // original list
    print(head);
  
    deleteNode(head, 20); // Call to delete function
    print(head); // 20 is not present thus no change in the
                 // list
  
    deleteNode(head, 10);
    print(head);
  
    deleteNode(head, 14);
    print(head);
  
    return 0;
}

输出：

Element not present in the list
15 14 12 10 
15 14 12 
15 12 

请参阅链表上的完整文章 |设置 3（删除节点）了解更多详情！