从双向链表中删除所有大于给定值的节点

给定一个包含 N 个节点和一个数字 X 的双向链表，任务是从列表中删除所有大于给定值 X 的节点。
例子：

Input: 10 8 4 11 9, X = 9 
Output: 8 4 9 
Explanation:  10 and 11 are greater than 9. So after removing them doubly linked list will become 8 4 9.
Input: 4 4 2 1 3 5, X = 2 
Output: 2 1

方法：将双向链表的节点一一遍历，得到数据值大于x的节点的指针。按照本文中使用的方法删除这些节点。

C++

// C++ implementation to delete all
// the nodes from the doubly
// linked list that are greater than
// the specified value x
#include 
 
using namespace std;
 
// Node of the doubly linked list
struct Node {
    int data;
    Node *prev, *next;
};
 
// function to insert a node at the beginning
// of the Doubly Linked List
void push(Node** head_ref, int new_data)
{
    // allocate node
    Node* new_node = (Node*)malloc(sizeof(struct Node));
 
    // put in the data
    new_node->data = new_data;
 
    // since we are adding at the beginning,
    // prev is always NULL
    new_node->prev = NULL;
 
    // link the old list off the new node
    new_node->next = (*head_ref);
 
    // change prev of head node to new node
    if ((*head_ref) != NULL)
        (*head_ref)->prev = new_node;
 
    // move the head to point to the new node
    (*head_ref) = new_node;
}
 
// function to delete a node in a Doubly Linked List.
// head_ref --> pointer to head node pointer.
// del  -->  pointer to node to be deleted
void deleteNode(Node** head_ref, Node* del)
{
    // base case
    if (*head_ref == NULL || del == NULL)
        return;
 
    // If node to be deleted is head node
    if (*head_ref == del)
        *head_ref = del->next;
 
    // Change next only if node to be
    // deleted is NOT the last node
    if (del->next != NULL)
        del->next->prev = del->prev;
 
    // Change prev only if node to be
    // deleted is NOT the first node
    if (del->prev != NULL)
        del->prev->next = del->next;
 
    // Finally, free the memory occupied by del
    free(del);
 
    return;
}
 
// function to delete all the nodes
// from the doubly linked
// list that are greater than the
// specified value x
void deleteGreaterNodes(Node** head_ref, int x)
{
    Node* ptr = *head_ref;
    Node* next;
 
    while (ptr != NULL) {
        next = ptr->next;
        // if true, delete node 'ptr'
        if (ptr->data > x)
            deleteNode(head_ref, ptr);
        ptr = next;
    }
}
 
// function to print nodes in a
// given doubly linked list
void printList(Node* head)
{
    while (head != NULL) {
        cout << head->data << " ";
        head = head->next;
    }
}
 
// Driver program to test above
int main()
{
    // start with the empty list
    Node* head = NULL;
 
    // create the doubly linked list
    // 10<->8<->4<->11<->9
    push(&head, 9);
    push(&head, 11);
    push(&head, 4);
    push(&head, 8);
    push(&head, 10);
 
    int x = 9;
 
    cout << "Original List: ";
    printList(head);
 
    deleteGreaterNodes(&head, x);
 
    cout << "\nModified List: ";
    printList(head);
}

Java

// Java implementation to delete all
// the nodes from the doubly
// linked list that are greater than
// the specified value x
class GFG
{
 
// Node of the doubly linked list
static class Node
{
    int data;
    Node prev, next;
};
 
// function to insert a node at the beginning
// of the Doubly Linked List
static Node push(Node head_ref, int new_data)
{
    // allocate node
    Node new_node = new Node();
 
    // put in the data
    new_node.data = new_data;
 
    // since we are adding at the beginning,
    // prev is always null
    new_node.prev = null;
 
    // link the old list off the new node
    new_node.next = (head_ref);
 
    // change prev of head node to new node
    if ((head_ref) != null)
        (head_ref).prev = new_node;
 
    // move the head to point to the new node
    (head_ref) = new_node;
     
    return head_ref;
}
 
// function to delete a node in a Doubly Linked List.
// head_ref -. pointer to head node pointer.
// del -. pointer to node to be deleted
static Node deleteNode(Node head_ref, Node del)
{
    // base case
    if (head_ref == null || del == null)
        return null;
 
    // If node to be deleted is head node
    if (head_ref == del)
        head_ref = del.next;
 
    // Change next only if node to be
    // deleted is NOT the last node
    if (del.next != null)
        del.next.prev = del.prev;
 
    // Change prev only if node to be
    // deleted is NOT the first node
    if (del.prev != null)
        del.prev.next = del.next;
 
    return head_ref;
}
 
// function to delete all the nodes
// from the doubly linked
// list that are greater than the
// specified value x
static Node deleteGreaterNodes(Node head_ref, int x)
{
    Node ptr = head_ref;
    Node next;
 
    while (ptr != null)
    {
        next = ptr.next;
         
        // if true, delete node 'ptr'
        if (ptr.data > x)
            deleteNode(head_ref, ptr);
        ptr = next;
    }
    return head_ref;
}
 
// function to print nodes in a
// given doubly linked list
static void printList(Node head)
{
    while (head != null)
    {
        System.out.print( head.data + " ");
        head = head.next;
    }
}
 
// Driver code
public static void main(String args[])
{
    // start with the empty list
    Node head = null;
 
    // create the doubly linked list
    // 10<.8<.4<.11<.9
    head = push(head, 9);
    head = push(head, 11);
    head = push(head, 4);
    head = push(head, 8);
    head = push(head, 10);
 
    int x = 9;
 
    System.out.print( "Original List: ");
    printList(head);
 
    head=deleteGreaterNodes(head, x);
 
    System.out.print( "\nModified List: ");
    printList(head);
}
}
 
// This code is contributed by Arnab Kundu

Python

# Python implementation to delete all
# the nodes from the doubly
# linked list that are greater than
# the specified value x
 
# Link list node
class Node:
     
    def __init__(self, data):
        self.data = data
        self.next = None
        self.prev = None
         
# function to insert a node at the beginning
# of the Doubly Linked List
def push( head_ref, new_data):
 
    # allocate node
    new_node = Node(0)
 
    # put in the data
    new_node.data = new_data
 
    # since we are adding at the beginning,
    # prev is always None
    new_node.prev = None
 
    # link the old list off the new node
    new_node.next = (head_ref)
 
    # change prev of head node to new node
    if ((head_ref) != None) :
        (head_ref).prev = new_node
 
    # move the head to point to the new node
    (head_ref) = new_node
     
    return head_ref;
 
# function to delete a node in a Doubly Linked List.
# head_ref -. pointer to head node pointer.
# del -. pointer to node to be deleted
def deleteNode(head_ref, del_) :
 
    # base case
    if (head_ref == None or del_ == None) :
        return head_ref
 
    # If node to be deleted is head node
    if (head_ref == del_) :
        head_ref = del_.next
 
    # Change next only if node to be
    # deleted is NOT the last node
    if (del_.next != None) :
        del_.next.prev = del_.prev
 
    # Change prev only if node to be
    # deleted is NOT the first node
    if (del_.prev != None) :
        del_.prev.next = del_.next
 
    return head_ref
 
# function to delete all the nodes
# from the doubly linked
# list that are greater than the
# specified value x
def deleteGreaterNodes(head_ref, x) :
 
    ptr = head_ref
    next = None
 
    while (ptr != None) :
        next = ptr.next
         
        # if true, delete node 'ptr'
        if (ptr.data > x) :
            head_ref = deleteNode(head_ref, ptr)
        ptr = next
         
    return head_ref;
 
# function to print nodes in a
# given doubly linked list
def printList( head) :
 
    while (head != None) :
        print( head.data, end= " ")
        head = head.next
 
# Driver program to test above
 
# start with the empty list
head = None
 
# create the doubly linked list
# 10<.8<.4<.11<.9
head = push(head, 9)
head = push(head, 11)
head = push(head, 4)
head = push(head, 8)
head = push(head, 10)
 
x = 9
 
print("Original List: ")
printList(head)
 
head = deleteGreaterNodes(head, x)
 
print("\nModified List: ")
printList(head)
 
# This code is contributed by Arnab Kundu

C#

// C# implementation to delete all
// the nodes from the doubly
// linked list that are greater than
// the specified value x
using System;
 
class GFG
{
  
// Node of the doubly linked list
public class Node
{
    public int data;
    public Node prev, next;
};
  
// function to insert a node at the beginning
// of the Doubly Linked List
static Node push(Node head_ref, int new_data)
{
    // allocate node
    Node new_node = new Node();
  
    // put in the data
    new_node.data = new_data;
  
    // since we are adding at the beginning,
    // prev is always null
    new_node.prev = null;
  
    // link the old list off the new node
    new_node.next = (head_ref);
  
    // change prev of head node to new node
    if ((head_ref) != null)
        (head_ref).prev = new_node;
  
    // move the head to point to the new node
    (head_ref) = new_node;
      
    return head_ref;
}
  
// function to delete a node in a Doubly Linked List.
// head_ref -. pointer to head node pointer.
// del -. pointer to node to be deleted
static Node deleteNode(Node head_ref, Node del)
{
    // base case
    if (head_ref == null || del == null)
        return null;
  
    // If node to be deleted is head node
    if (head_ref == del)
        head_ref = del.next;
  
    // Change next only if node to be
    // deleted is NOT the last node
    if (del.next != null)
        del.next.prev = del.prev;
  
    // Change prev only if node to be
    // deleted is NOT the first node
    if (del.prev != null)
        del.prev.next = del.next;
  
    return head_ref;
}
  
// function to delete all the nodes
// from the doubly linked
// list that are greater than the
// specified value x
static Node deleteGreaterNodes(Node head_ref, int x)
{
    Node ptr = head_ref;
    Node next;
  
    while (ptr != null)
    {
        next = ptr.next;
          
        // if true, delete node 'ptr'
        if (ptr.data > x)
            deleteNode(head_ref, ptr);
        ptr = next;
    }
    return head_ref;
}
  
// function to print nodes in a
// given doubly linked list
static void printList(Node head)
{
    while (head != null)
    {
        Console.Write( head.data + " ");
        head = head.next;
    }
}
  
// Driver code
public static void Main(String []args)
{
    // start with the empty list
    Node head = null;
  
    // create the doubly linked list
    // 10<.8<.4<.11<.9
    head = push(head, 9);
    head = push(head, 11);
    head = push(head, 4);
    head = push(head, 8);
    head = push(head, 10);
  
    int x = 9;
  
    Console.Write( "Original List: ");
    printList(head);
  
    head=deleteGreaterNodes(head, x);
  
    Console.Write( "\nModified List: ");
    printList(head);
}
}
 
// This code contributed by Rajput-Ji

Javascript

// Javascript implementation to delete all
// the nodes from the doubly
// linked list that are greater than
// the specified value x
 
// Node of the doubly linked list
class Node
{
    constructor()
    {
        this.prev = null;
        this.next = null;
        this.data = 0;
    }
}
 
// function to insert a node at the beginning
// of the Doubly Linked List
function push(head_ref,new_data)
{
    // allocate node
    let new_node = new Node();
  
    // put in the data
    new_node.data = new_data;
  
    // since we are adding at the beginning,
    // prev is always null
    new_node.prev = null;
  
    // link the old list off the new node
    new_node.next = (head_ref);
  
    // change prev of head node to new node
    if ((head_ref) != null)
        (head_ref).prev = new_node;
  
    // move the head to point to the new node
    (head_ref) = new_node;
      
    return head_ref;
}
 
// function to delete a node in a Doubly Linked List.
// head_ref -. pointer to head node pointer.
// del -. pointer to node to be deleted
function deleteNode(head_ref,del)
{
    // base case
    if (head_ref == null || del == null)
        return null;
  
    // If node to be deleted is head node
    if (head_ref == del)
        head_ref = del.next;
  
    // Change next only if node to be
    // deleted is NOT the last node
    if (del.next != null)
        del.next.prev = del.prev;
  
    // Change prev only if node to be
    // deleted is NOT the first node
    if (del.prev != null)
        del.prev.next = del.next;
  
    return head_ref;
}
 
// function to delete all the nodes
// from the doubly linked
// list that are greater than the
// specified value x
function deleteGreaterNodes(head_ref,x)
{
    let ptr = head_ref;
    let next;
  
    while (ptr != null)
    {
        next = ptr.next;
          
        // if true, delete node 'ptr'
        if (ptr.data > x)
            deleteNode(head_ref, ptr);
        ptr = next;
    }
    return head_ref;
}
 
// function to print nodes in a
// given doubly linked list
function printList(head)
{
    while (head != null)
    {
        document.write( head.data + " ");
        head = head.next;
    }
}
 
// Driver code
// start with the empty list
let head = null;
 
// create the doubly linked list
// 10<.8<.4<.11<.9
head = push(head, 9);
head = push(head, 11);
head = push(head, 4);
head = push(head, 8);
head = push(head, 10);
 
let x = 9;
 
document.write( "Original List: ");
printList(head);
 
head=deleteGreaterNodes(head, x);
 
document.write( "<br>Modified List: ");
printList(head);
 
// This code is contributed by avanitrachhadiya2155

输出：

Original List: 10 8 4 11 9 
Modified List: 8 4 9

时间复杂度： O(N)
辅助空间： O(1)

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