Insert value in sorted way in a sorted doubly linked list
Last Updated : 04 Sep, 2024
Given a Sorted Doubly Linked List in (non-decreasing order) and an element x, the task is to insert the element x into the correct position in the Sorted Doubly Linked List.
Example:
Input: LinkedList = 3<->5<->8<->10<->12 , x = 9
Output: 3<->5<->8<->9<->10<->12
Explanation: Here node 9 is inserted between 8 and 10 in the Doubly Linked-List.
Input: LinkedList = 1<->4<->10<->11 , x = 15
Output: 1<->4<->10<->11<->15
Explanation: Here node 15 is inserted at end in the Doubly Linked-List.
Approach:
To insert a value into a sorted doubly linked list while maintaining sorted order, start by creating a new node with the given value.
- If the list is empty, new node becomes the head of the doubly linked list.
- else If the new node's value is smaller than or equal to the head's value, insert it at the beginning.
- else, traverse the list to find the correct position where the new node’s value is greater than the current node and smaller than the next node. Adjust pointers to insert the node between the current and next node or after the current node (if curr's next is NULL) .
C++ // C++ implementation to insert value in sorted way // in a sorted doubly linked list #include <iostream> using namespace std; class Node { public: int data; Node* prev; Node* next; Node(int new_data) { data = new_data; prev = nullptr; next = nullptr; } }; // Function to insert element x into sorted DLL Node* sortedInsert(Node* head, int x) { // Create a new node with the given data Node* newNode = new Node(x); // If the list is empty, set new node as the head if (head == nullptr) { return newNode; } // If new node needs to be inserted at beginning if (x <= head->data) { newNode->next = head; head->prev = newNode; return newNode; } // Traverse the list to find correct position Node* curr = head; while (curr->next != nullptr && curr->next->data < x) { curr = curr->next; } // Insert the new node in the correct position newNode->next = curr->next; if (curr->next != nullptr) { curr->next->prev = newNode; } curr->next = newNode; newNode->prev = curr; return head; } void printList(Node* curr) { while (curr != nullptr) { cout << curr->data << " "; curr = curr->next; } } int main() { // Create hardcoded DLL: // 3 <-> 5 <-> 8 <-> 10 <-> 12 Node* head = new Node(3); head->next = new Node(5); head->next->prev = head; head->next->next = new Node(8); head->next->next->prev = head->next; head->next->next->next = new Node(10); head->next->next->next->prev = head->next->next; head->next->next->next->next = new Node(12); head->next->next->next->next->prev = head->next->next->next; int x = 9; head = sortedInsert(head, x); printList(head); return 0; } // C implementation to insert value in sorted way // in a sorted doubly linked list #include <stdio.h> #include <stdlib.h> struct Node { int data; struct Node *prev, *next; }; struct Node *createNode(int data); // Function to insert an element x into the correct // position in a sorted doubly linked list struct Node *sortedInsert(struct Node *head, int x) { // Create a new node with the given data struct Node *newNode = createNode(x); // If the list is empty, return the new node // as the head if (head == NULL) { return newNode; } // If the new node needs to be inserted at the // beginning if (x <= head->data) { newNode->next = head; head->prev = newNode; return newNode; } // Traverse the list to find the correct position // to insert the new node struct Node *curr = head; while (curr->next != NULL && curr->next->data < x) { curr = curr->next; } // Insert the new node in the // correct position newNode->next = curr->next; if (curr->next != NULL) { curr->next->prev = newNode; } curr->next = newNode; newNode->prev = curr; return head; } void printList(struct Node *curr) { while (curr != NULL) { printf("%d ", curr->data); curr = curr->next; } } struct Node *createNode(int data) { struct Node *newNode = (struct Node *)malloc(sizeof(struct Node)); newNode->data = data; newNode->prev = newNode->next = NULL; return newNode; } int main() { // Create a hardcoded doubly linked list: // 3 <-> 5 <-> 8 <-> 10 <-> 12 struct Node *head = createNode(3); head->next = createNode(5); head->next->prev = head; head->next->next = createNode(8); head->next->next->prev = head->next; head->next->next->next = createNode(10); head->next->next->next->prev = head->next->next; head->next->next->next->next = createNode(12); head->next->next->next->next->prev = head->next->next->next; int x = 9; head = sortedInsert(head, x); printList(head); return 0; } // Java implementation to insert value in sorted way // in a sorted doubly linked list class Node { int data; Node prev, next; Node(int data) { this.data = data; this.prev = null; this.next = null; } } public class GfG { // Function to insert an element x into the // correct position in a sorted doubly linked list static Node sortedInsert(Node head, int x) { // Create a new node with the given data Node newNode = new Node(x); // If the list is empty, return the new node // as the head if (head == null) { return newNode; } // If the new node needs to be inserted at // the beginning if (x <= head.data) { newNode.next = head; head.prev = newNode; return newNode; } // Traverse the list to find the correct // position to insert the new node Node curr = head; while (curr.next != null && curr.next.data < x) { curr = curr.next; } // Insert the new node in the correct position newNode.next = curr.next; if (curr.next != null) { curr.next.prev = newNode; } curr.next = newNode; newNode.prev = curr; return head; } static void printList(Node curr) { while (curr != null) { System.out.print(curr.data + " "); curr = curr.next; } } public static void main(String[] args) { // Create a hardcoded doubly linked list: // 3 <-> 5 <-> 8 <-> 10 <-> 12 Node head = new Node(3); head.next = new Node(5); head.next.prev = head; head.next.next = new Node(8); head.next.next.prev = head.next; head.next.next.next = new Node(10); head.next.next.next.prev = head.next.next; head.next.next.next.next = new Node(12); head.next.next.next.next.prev = head.next.next.next; int x = 9; head = sortedInsert(head, x); printList(head); } } # Python implementation to insert value in sorted way # in a sorted doubly linked list class Node: def __init__(self, data): self.data = data self.prev = None self.next = None # Function to insert an element x into the correct # position in a sorted doubly linked list def sorted_insert(head, x): # Create a new node with the given data new_node = Node(x) # If the list is empty, return the new node # as the head if head is None: return new_node # If the new node needs to be inserted at # the beginning if x <= head.data: new_node.next = head head.prev = new_node return new_node # Traverse the list to find the correct # position to insert the new node curr = head while curr.next is not None and curr.next.data < x: curr = curr.next # Insert the new node in the correct position new_node.next = curr.next if curr.next is not None: curr.next.prev = new_node curr.next = new_node new_node.prev = curr return head def print_list(curr): while curr is not None: print(curr.data, end=" ") curr = curr.next print() if __name__ == "__main__": # Create a hardcoded doubly linked list: # 3 <-> 5 <-> 8 <-> 10 <-> 12 head = Node(3) head.next = Node(5) head.next.prev = head head.next.next = Node(8) head.next.next.prev = head.next head.next.next.next = Node(10) head.next.next.next.prev = head.next.next head.next.next.next.next = Node(12) head.next.next.next.next.prev = head.next.next.next x = 9 head = sorted_insert(head, x) print_list(head)
// C# implementation to insert value in sorted way // in a sorted doubly linked list using System; class Node { public int data; public Node prev, next; public Node(int data) { this.data = data; this.prev = null; this.next = null; } } class GfG { // Function to insert an element x into the // correct position in a sorted doubly linked list static Node SortedInsert(Node head, int x) { // Create a new node with the given data Node newNode = new Node(x); // If the list is empty, return the new node // as the head if (head == null) { return newNode; } // If the new node needs to be inserted at // the beginning if (x <= head.data) { newNode.next = head; head.prev = newNode; return newNode; } // Traverse the list to find the correct // position to insert the new node Node curr = head; while (curr.next != null && curr.next.data < x) { curr = curr.next; } // Insert the new node in the correct position newNode.next = curr.next; if (curr.next != null) { curr.next.prev = newNode; } curr.next = newNode; newNode.prev = curr; return head; } static void PrintList(Node curr) { while (curr != null) { Console.Write(curr.data + " "); curr = curr.next; } Console.WriteLine(); } static void Main() { // Create a hardcoded doubly linked list: // 3 <-> 5 <-> 8 <-> 10 <-> 12 Node head = new Node(3); head.next = new Node(5); head.next.prev = head; head.next.next = new Node(8); head.next.next.prev = head.next; head.next.next.next = new Node(10); head.next.next.next.prev = head.next.next; head.next.next.next.next = new Node(12); head.next.next.next.next.prev = head.next.next.next; int x = 9; head = SortedInsert(head, x); PrintList(head); } } // JavaScript implementation to insert value // in sorted way in a sorted doubly linked list class Node { constructor(data) { this.data = data; this.prev = null; this.next = null; } } // Function to insert an element x into the correct // position in a sorted doubly linked list function sortedInsert(head, x) { // Create a new node with the given data const newNode = new Node(x); // If the list is empty, return the new node // as the head if (head === null) { return newNode; } // If the new node needs to be inserted at // the beginning if (x <= head.data) { newNode.next = head; head.prev = newNode; return newNode; } // Traverse the list to find the correct // position to insert the new node let curr = head; while (curr.next !== null && curr.next.data < x) { curr = curr.next; } // Insert the new node in the correct position newNode.next = curr.next; if (curr.next !== null) { curr.next.prev = newNode; } curr.next = newNode; newNode.prev = curr; return head; } function printList(curr) { while (curr !== null) { process.stdout.write(curr.data + " "); curr = curr.next; } console.log(); } // Create a hardcoded doubly linked list: // 3 <-> 5 <-> 8 <-> 10 <-> 12 let head = new Node(3); head.next = new Node(5); head.next.prev = head; head.next.next = new Node(8); head.next.next.prev = head.next; head.next.next.next = new Node(10); head.next.next.next.prev = head.next.next; head.next.next.next.next = new Node(12); head.next.next.next.next.prev = head.next.next.next; const x = 9; head = sortedInsert(head, x); printList(head); Time Complexity: O(n) , where n is the number of nodes in the linked lsit.
Auxiliary Space: O(1)
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