Cpp

/* * Doubly linked list implementation in c++. * operations: * 1-> Insert at head. * 2-> print forward. * 3-> print reverse order. */ #include<iostream> using namespace std; struct node { int data; node* next; node* prev; }; class d_list { private: node* head; node* GetNewNode(int n) { node* newNode = new node(); newNode->data = n; newNode->next = NULL; newNode->prev = NULL; return newNode; } public: d_list() { head = NULL; } void InsertAtHead(int n) { node* temp = GetNewNode(n); if (head == NULL) { head = temp; return; } head->prev = temp; temp->next = head; head = temp; } void print() { node* t = head; cout << "Forward: "; while (t!=NULL) { cout << t->data << " "; t = t->next; } cout << " "; } void print_reverse() { node* t = head; while (t->next != NULL) { t = t->next; } //reverse cout << "reverse: "; while (t != NULL) { cout << t->data << " "; t = t->prev; } cout << " "; } }; int main() { d_list l; //object from class doubly list l.InsertAtHead(1); l.InsertAtHead(2); //function insert at beginning l.InsertAtHead(3); l.print(); //List should print: 3 2 1 l.print_reverse(); //List should print: 1 2 3 return 0; }

#include<iostream> using namespace std; class node{ private: int data; node *next; node *prev; public: void insertData(); void printData(); }; node *head=0; void node::insertData() { int d; head=new node(); cout<<"Enter data : "; cin>>d; head->prev=0; head->data=d; head->next=0; node *top; top=head; node *newnode; int c=0; cout<<"Do you want to continue if yes press 1 else press : "; cin>>c; while (c==1) { newnode=new node(); cout<<"Enter data : "; cin>>newnode->data; newnode->next=0; newnode->prev=0; top->next=newnode; top=top->next; cout<<"Do you want to continue if yes press 1 and press 2 : "; cin>>c; } } void node::printData() { node *top; top=head; while(top!=0) { cout<<top->data<<" "; top=top->next; } } int main() { node obj; obj.insertData(); obj.printData(); }

#include <iostream> #include <list> // For help in printing lists std::ostream& operator<<(std::ostream& ostr, const std::list<int>& list) { for (const auto &i : list) { ostr << ' ' << i; } return ostr; } int main() { std::list<int> list1 = { 5,9,1,3,3 }; std::list<int> list2 = { 8,7,2,3,4,4 }; list1.sort(); list2.sort(); std::cout << "list1: " << list1 << ' '; std::cout << "list2: " << list2 << ' '; list1.merge(list2); std::cout << "merged: " << list1 << ' '; return 0; }

// A complete working C++ program to
// demonstrate all insertion methods
#include <bits/stdc++.h>
using namespace std;
 
// A linked list node
class Node
{
    public:
    int data;
    Node* next;
    Node* prev;
};
 
/* 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)
{
    /* 1. allocate node */
    Node* new_node = new Node();
 
    /* 2. put in the data */
    new_node->data = new_data;
 
    /* 3. Make next of new node as head
    and previous as NULL */
    new_node->next = (*head_ref);
    new_node->prev = NULL;
 
    /* 4. change prev of head node to new node */
    if ((*head_ref) != NULL)
        (*head_ref)->prev = new_node;
 
    /* 5. move the head to point to the new node */
    (*head_ref) = new_node;
}
 
/* Given a node as prev_node, insert
a new node after the given node */
void insertAfter(Node* prev_node, int new_data)
{
    /*1. check if the given prev_node is NULL */
    if (prev_node == NULL)
    {
        cout<<"the given previous node cannot be NULL";
        return;
    }
 
    /* 2. allocate new node */
    Node* new_node = new Node();
 
    /* 3. put in the data */
    new_node->data = new_data;
 
    /* 4. Make next of new node as next of prev_node */
    new_node->next = prev_node->next;
 
    /* 5. Make the next of prev_node as new_node */
    prev_node->next = new_node;
 
    /* 6. Make prev_node as previous of new_node */
    new_node->prev = prev_node;
 
    /* 7. Change previous of new_node's next node */
    if (new_node->next != NULL)
        new_node->next->prev = new_node;
}
 
/* Given a reference (pointer to pointer) to the head
of a DLL and an int, appends a new node at the end */
void append(Node** head_ref, int new_data)
{
    /* 1. allocate node */
    Node* new_node = new Node();
 
    Node* last = *head_ref; /* used in step 5*/
 
    /* 2. put in the data */
    new_node->data = new_data;
 
    /* 3. This new node is going to be the last node, so
        make next of it as NULL*/
    new_node->next = NULL;
 
    /* 4. If the Linked List is empty, then make the new
        node as head */
    if (*head_ref == NULL)
    {
        new_node->prev = NULL;
        *head_ref = new_node;
        return;
    }
 
    /* 5. Else traverse till the last node */
    while (last->next != NULL)
        last = last->next;
 
    /* 6. Change the next of last node */
    last->next = new_node;
 
    /* 7. Make last node as previous of new node */
    new_node->prev = last;
 
    return;
}
 
// This function prints contents of
// linked list starting from the given node
void printList(Node* node)
{
    Node* last;
    cout<<"
Traversal in forward direction 
";
    while (node != NULL)
    {
        cout<<" "<<node->data<<" ";
        last = node;
        node = node->next;
    }
 
    cout<<"
Traversal in reverse direction 
";
    while (last != NULL)
    {
        cout<<" "<<last->data<<" ";
        last = last->prev;
    }
}
 
/* Driver program to test above functions*/
int main()
{
    /* Start with the empty list */
    Node* head = NULL;
 
    // Insert 6. So linked list becomes 6->NULL
    append(&head, 6);
 
    // Insert 7 at the beginning. So
    // linked list becomes 7->6->NULL
    push(&head, 7);
 
    // Insert 1 at the beginning. So
    // linked list becomes 1->7->6->NULL
    push(&head, 1);
 
    // Insert 4 at the end. So linked
    // list becomes 1->7->6->4->NULL
    append(&head, 4);
 
    // Insert 8, after 7. So linked
    // list becomes 1->7->8->6->4->NULL
    insertAfter(head->next, 8);
 
    cout << "Created DLL is: ";
    printList(head);
 
    return 0;
}
 
// This is code is contributed by rathbhupendra