136 lines
3.1 KiB
C++
136 lines
3.1 KiB
C++
/*A node can be added in three ways
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1) At the front of the linked list
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2) After a given node.
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3) At the end of the linked list.*/
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// all insertion methods on Linked List
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#include <bits/stdc++.h>
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using namespace std;
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// A linked list node
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class Node
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{
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public:
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int data;
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Node *next;
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};
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/* Given a reference (pointer to pointer)
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to the head of a list and an int, inserts
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a new node on the front of the list. */
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void push(Node** head_ref, int new_data)
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{
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/* 1. allocate node */
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Node* new_node = new Node();
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/* 2. put in the data */
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new_node->data = new_data;
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/* 3. Make next of new node as head */
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new_node->next = (*head_ref);
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/* 4. move the head to point to the new node */
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(*head_ref) = new_node;
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}
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/* Given a node prev_node, insert a new node after the given
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prev_node */
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void insertAfter(Node* prev_node, int new_data)
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{
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/*1. check if the given prev_node is NULL */
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if (prev_node == NULL)
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{
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cout<<"the given previous node cannot be NULL";
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return;
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}
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/* 2. allocate new node */
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Node* new_node = new Node();
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/* 3. put in the data */
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new_node->data = new_data;
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/* 4. Make next of new node as next of prev_node */
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new_node->next = prev_node->next;
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/* 5. move the next of prev_node as new_node */
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prev_node->next = new_node;
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}
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/* Given a reference (pointer to pointer) to the head
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of a list and an int, appends a new node at the end */
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void append(Node** head_ref, int new_data)
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{
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/* 1. allocate node */
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Node* new_node = new Node();
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Node *last = *head_ref; /* used in step 5*/
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/* 2. put in the data */
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new_node->data = new_data;
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/* 3. This new node is going to be
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the last node, so make next of
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it as NULL*/
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new_node->next = NULL;
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/* 4. If the Linked List is empty,
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then make the new node as head */
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if (*head_ref == NULL)
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{
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*head_ref = new_node;
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return;
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}
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/* 5. Else traverse till the last node */
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while (last->next != NULL)
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last = last->next;
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/* 6. Change the next of last node */
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last->next = new_node;
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return;
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}
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// This function prints contents of
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// linked list starting from head
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void printList(Node *node)
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{
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while (node != NULL)
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{
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cout<<" "<<node->data;
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node = node->next;
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}
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}
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/* Driver code*/
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int main()
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{
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/* Start with the empty list */
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Node* head = NULL;
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// Insert 6. So linked list becomes 6->NULL
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append(&head, 6);
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// Insert 7 at the beginning.
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// So linked list becomes 7->6->NULL
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push(&head, 7);
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// Insert 1 at the beginning.
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// So linked list becomes 1->7->6->NULL
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push(&head, 1);
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// Insert 4 at the end. So
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// linked list becomes 1->7->6->4->NULL
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append(&head, 4);
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// Insert 8, after 7. So linked
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// list becomes 1->7->8->6->4->NULL
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insertAfter(head->next, 8);
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cout<<"Created Linked list is: ";
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printList(head);
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return 0;
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}
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