Given a sorted doubly linked list and a value to insert, write a function to insert the value in sorted way.

Initial doubly linked list

Doubly Linked List after insertion of 9

**Algorithm:**

Let input doubly linked list is sorted in increasing order.

New node passed to the function contains data in the data part and previous and next link are set to NULL.

sortedInsert(head_ref, newNode)if (head_ref == NULL) head_ref = newNode else if head_ref->data >= newNode->data newNode->next = head_ref newNode->next->prev = newNode head_ref = newNode else Initialize current = head_ref while (current->next != NULL and current->next->data data) current = current->next newNode->next = current->next if current->next != NULL newNode->next->prev = newNode current->next = newNode newNode->prev = current

// C++ implementation to insert value in sorted way // in a sorted doubly linked list #include <bits/stdc++.h> using namespace std; // Node of a doubly linked list struct Node { int data; struct Node* prev, *next; }; // function to create and return a new node // of a doubly linked list struct Node* getNode(int data) { // allocate node struct Node* newNode = (struct Node*)malloc(sizeof(struct Node)); // put in the data newNode->data = data; newNode->prev = newNode->next = NULL; return newNode; } // function to insert a new node in sorted way in // a sorted doubly linked list void sortedInsert(struct Node** head_ref, struct Node* newNode) { struct Node* current; // if list is empty if (*head_ref == NULL) *head_ref = newNode; // if the node is to be inserted at the beginning // of the doubly linked list else if ((*head_ref)->data >= newNode->data) { newNode->next = *head_ref; newNode->next->prev = newNode; *head_ref = newNode; } else { current = *head_ref; // locate the node after which the new node // is to be inserted while (current->next != NULL && current->next->data < newNode->data) current = current->next; /* Make the appropriate links */ newNode->next = current->next; // if the new node is not inserted // at the end of the list if (current->next != NULL) newNode->next->prev = newNode; current->next = newNode; newNode->prev = current; } } // function to print the doubly linked list void printList(struct Node* head) { while (head != NULL) { cout << head->data << " "; head = head->next; } } // Driver program to test above int main() { /* start with the empty doubly linked list */ struct Node* head = NULL; // insert the following nodes in sorted way struct Node* new_node = getNode(8); sortedInsert(&head, new_node); new_node = getNode(5); sortedInsert(&head, new_node); new_node = getNode(3); sortedInsert(&head, new_node); new_node = getNode(10); sortedInsert(&head, new_node); new_node = getNode(12); sortedInsert(&head, new_node); new_node = getNode(9); sortedInsert(&head, new_node); cout << "Created Doubly Linked Listn"; printList(head); return 0; }

Output:

Created Doubly Linked List 3 5 8 9 10 12

Time Complexity: O(n)

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