Search an element in a Doubly Linked List
Given a Doubly linked list(DLL) containing N nodes and an integer X, the task is to find the position of the integer X in the doubly linked list. If no such position found then print -1.
Examples:
Input: 15 <=> 16 <=> 8 <=> 7 <=> 13, X = 8
Output: 3
Explanation: X (= 8) is present at the 3rd node of the doubly linked list.
Therefore, the required output is 3Input: 5 <=> 3 <=> 4 <=> 2 <=> 9, X = 0
Output: -1
Explanation: X (= 0) is not present in the doubly linked list.
Therefore, the required output is -1
Approach: Follow the steps below to solve the problem:
- Initialize a variable, say pos, to store the position of the node containing data value X in the doubly linked list.
- Initialize a pointer, say temp, to store the head node of the doubly linked list.
- Iterate over the linked list and for every node, check if data value of that node is equal to X or not. If found to be true, then print pos.
- Otherwise, print -1.
Below is the implementation of the above approach
C++
// C++ program to implement// the above approach#include <bits/stdc++.h>using namespace std;// Structure of a node of// the doubly linked liststruct Node { // Stores data value // of a node int data; // Stores pointer // to next node Node* next; // Stores pointer // to previous node Node* prev;};// Function to insert a node at the// beginning of the Doubly Linked Listvoid push(Node** head_ref, int new_data){ // Allocate memory for new node Node* new_node = (Node*)malloc(sizeof(struct Node)); // Insert the data new_node->data = new_data; // Since node is added at the // beginning, prev is always NULL new_node->prev = NULL; // Link the old list to the new node new_node->next = (*head_ref); // If pointer to head is not NULL if ((*head_ref) != NULL) { // Change the prev of head // node to new node (*head_ref)->prev = new_node; } // Move the head to point to the new node (*head_ref) = new_node;}// Function to find the position of// an integer in doubly linked listint search(Node** head_ref, int x){ // Stores head Node Node* temp = *head_ref; // Stores position of the integer // in the doubly linked list int pos = 0; // Traverse the doubly linked list while (temp->data != x && temp->next != NULL) { // Update pos pos++; // Update temp temp = temp->next; } // If the integer not present // in the doubly linked list if (temp->data != x) return -1; // If the integer present in // the doubly linked list return (pos + 1);}// Driver Codeint main(){ Node* head = NULL; int X = 8; // Create the doubly linked list // 18 <-> 15 <-> 8 <-> 9 <-> 14 push(&head, 14); push(&head, 9); push(&head, 8); push(&head, 15); push(&head, 18); cout << search(&head, X); return 0;} |
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Java
// Java program to implement// the above approachimport java.util.*;class GFG{ // Structure of a node of // the doubly linked list static class Node { // Stores data value // of a node int data; // Stores pointer // to next node Node next; // Stores pointer // to previous node Node prev; }; // Function to insert a node at the // beginning of the Doubly Linked List static Node push(Node head_ref, int new_data) { // Allocate memory for new node Node new_node = new Node(); // Insert the data new_node.data = new_data; // Since node is added at the // beginning, prev is always null new_node.prev = null; // Link the old list to the new node new_node.next = head_ref; // If pointer to head is not null if (head_ref != null) { // Change the prev of head // node to new node head_ref.prev = new_node; } // Move the head to point to the new node head_ref = new_node; return head_ref; } // Function to find the position of // an integer in doubly linked list static int search(Node head_ref, int x) { // Stores head Node Node temp = head_ref; // Stores position of the integer // in the doubly linked list int pos = 0; // Traverse the doubly linked list while (temp.data != x && temp.next != null) { // Update pos pos++; // Update temp temp = temp.next; } // If the integer not present // in the doubly linked list if (temp.data != x) return -1; // If the integer present in // the doubly linked list return (pos + 1); } // Driver Code public static void main(String[] args) { Node head = null; int X = 8; // Create the doubly linked list // 18 <-> 15 <-> 8 <-> 9 <-> 14 head = push(head, 14); head = push(head, 9); head = push(head, 8); head = push(head, 15); head = push(head, 18); System.out.print(search(head, X)); }}// This code is contributed by Rajput-Ji |
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C#
// C# program to implement// the above approachusing System;class GFG{ // Structure of a node of// the doubly linked listpublic class Node { // Stores data value // of a node public int data; // Stores pointer // to next node public Node next; // Stores pointer // to previous node public Node prev;};// Function to insert a node at the// beginning of the Doubly Linked Liststatic Node push(Node head_ref, int new_data){ // Allocate memory for new node Node new_node = new Node(); // Insert the data new_node.data = new_data; // Since node is added at the // beginning, prev is always null new_node.prev = null; // Link the old list to the new node new_node.next = head_ref; // If pointer to head is not null if (head_ref != null) { // Change the prev of head // node to new node head_ref.prev = new_node; } // Move the head to point to the new node head_ref = new_node; return head_ref;}// Function to find the position of// an integer in doubly linked liststatic int search(Node head_ref, int x){ // Stores head Node Node temp = head_ref; // Stores position of the integer // in the doubly linked list int pos = 0; // Traverse the doubly linked list while (temp.data != x && temp.next != null) { // Update pos pos++; // Update temp temp = temp.next; } // If the integer not present // in the doubly linked list if (temp.data != x) return -1; // If the integer present in // the doubly linked list return (pos + 1);}// Driver Codepublic static void Main(String[] args){ Node head = null; int X = 8; // Create the doubly linked list // 18 <-> 15 <-> 8 <-> 9 <-> 14 head = push(head, 14); head = push(head, 9); head = push(head, 8); head = push(head, 15); head = push(head, 18); Console.Write(search(head, X));}}// This code is contributed by gauravrajput1 |
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Output:
3
Time Complexity: O(N)
Auxiliary Space: O(1)
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