Linked Lists: Program 7 to 11

Author: deltanode

26_linked_lists/07_input.txt

@@ -0,0 +1,8 @@
+4
+5
+9
+10
+3
+19
+7
+-1

26_linked_lists/07_linked_list_taking_input.cpp

@@ -0,0 +1,302 @@
+/*
+    TOPIC: Linked List - Taking Input
+
+    - Taking input from user
+    - Taking input from file
+*/
+
+#include <iostream>
+using namespace std;
+
+class Node{
+public:
+    int data;
+    Node *next;
+
+    // constructor
+    Node(int d)
+    {
+        data = d;
+        next = NULL;
+    }
+};
+
+
+// pass a pointer by reference (because we want to make changes to the original head pointer)
+void insertAtHead(Node *&head, int d)
+{
+    if(head == NULL)
+    {
+        head = new Node(d);
+        return;
+    }
+
+    Node *n = new Node(d);
+    n->next = head;
+    head = n;
+}
+
+
+
+// function to find length of linked list
+int length(Node*head)
+{
+    int cnt = 0;
+    while(head != NULL)
+    {
+        cnt++;
+        head = head->next;
+    }
+    return cnt;
+}
+
+
+
+// function to insert data at last position of linked list
+void insertAtTail(Node*&head, int data)
+{
+    // corner case
+    if(head == NULL)
+    {
+        // Node *n =  new Node(data);
+        // head = n;
+        head = new Node(data);
+        return;
+    }
+    Node *tail = head;             // using temp pointer
+    // Moving head towards tail
+    while(tail->next != NULL)
+    {
+        tail = tail->next;
+    }
+    // create & attach new node
+    tail->next = new Node(data);
+}
+
+
+
+// function to insert data at middle of linked list
+void insertAtMiddle(Node*&head, int data, int pos)
+{
+    //corner case
+    if(head==NULL or pos==0)
+    {
+        insertAtHead(head, data);
+        return;
+    }
+    else if (pos >= length(head))
+    {
+        insertAtTail(head, data);
+        return;
+    }
+    // take pos-1 jumps
+    int i=1;
+    Node *temp = head;
+    while(i < pos)
+    {
+        temp = temp->next;
+        i++;
+    }
+    // create a new node
+    Node *n = new Node(data);
+    n->next = temp->next;
+    temp->next = n;
+}
+
+// pass by value (because we don't want to change the original head pointer)
+void print(Node *head)
+{
+    while(head != NULL)
+    {
+        cout << head->data << " -> ";
+        head = head->next;
+    }
+    cout << endl;
+}
+
+
+
+// function to delete data at start of linked list
+void deleteAtHead(Node*&head)
+{
+    if(head == NULL)
+    {
+        return;
+    }
+    Node*temp = head->next;   // temp pointer is static. So it will be deleted at the end of function call 
+    delete head;              // delete the Node whose address is stored in "head" pointer
+    head = temp;
+}
+
+
+
+// function to delete data at end of linked list
+void deleteAtTail(Node*&head)
+{
+    if(head == NULL)
+    {
+        return;
+    }
+    Node *tail = head;
+    Node *prev;
+    // moving towards the end of linked list
+    while(tail->next != NULL)
+    {
+        prev = tail;
+        tail = tail->next;
+    }
+    delete tail;                  // delete the Node whose address is stored in "tail" pointer
+    // delete prev->next;         // prev->nex & tail are pointing towards same address
+    prev->next = NULL;
+}
+
+
+
+// function to delete data at end of linked list
+void deleteAtMiddle(Node*&head, int pos)
+{
+    if(head==NULL)
+    {
+        return;
+    }
+    else if(pos >= length(head))
+    {
+        return;
+    }
+    // jump towards pos
+    Node *temp = head;
+    Node *prev;
+    int i = 1;
+    while(i <= pos)
+    {
+        prev = temp;
+        temp = temp->next;
+        i++;
+    }
+    prev->next = temp->next;
+    delete temp;              // delete the Node whose address is stored in "temp" pointer
+}
+
+
+// Search Operation
+// Linear Search
+bool search(Node*head, int key)
+{
+    Node*temp = head;
+    while(temp != NULL)
+    {
+        if(temp->data == key)
+        {
+            return true;
+        }
+        temp = temp->next;
+    }
+    // if key not found
+    return false;
+}
+
+
+// Linear Search (recursively)
+bool searchRecursive(Node*head, int key)
+{
+    //base case
+    if(head == NULL)
+    { 
+        return false;
+    }
+    //rec case
+    if(head->data == key)
+    {
+        return true;
+    }
+    return searchRecursive(head->next, key);
+}
+
+
+// Linked List User Input
+void take_input(Node*&head)
+{
+    //
+}
+
+// Linked List User Input
+Node* take_input_2()
+{
+    Node *head = NULL;
+
+    int data;
+    cin >> data;
+
+    while(data != -1)
+    {
+        insertAtHead(head, data);
+        // insertAtTail(head, data);
+        cin >> data;
+    }
+    return head;
+    /* NOTE: Since we are adding elements at "head" of linked list.
+             So, we will be getting linked list in the reverse order.
+    */
+}
+
+
+// Linked List User Input [When taking Input from a file]
+Node* take_input_file()
+{
+    Node *head = NULL;
+
+    int data;
+    // cin >> data;
+
+    while(cin >> data)
+    // while(data != -1)
+    {
+        insertAtHead(head, data);
+        // cin >> data;
+    }
+    return head;
+    /* NOTE: Since we are adding elements at "head" of linked list.
+             So, we will be getting linked list in the reverse order.
+    */
+}
+
+
+
+int main()
+{
+    // since we don't have linked list class, we have to keep the track of head pointer
+    Node *head = NULL;        // to store address of the first node
+
+    /*     
+    insertAtHead(head,3);
+    insertAtHead(head,9);
+    insertAtHead(head,74);
+    insertAtMiddle(head,44,3);
+    insertAtTail(head,88);
+    */
+
+    // take input of linked list from user
+    cout << "Enter Elements [Press -1 to Exit]: ";
+    head = take_input_2();
+
+    // // take input from file "input.txt"
+    // head = take_input_file();
+
+    cout << "Linked List: ";
+    print(head);
+
+    return 0;
+}
+
+
+/* 
+OUTPUT:
+
+Case 1: [Input from USER]
+    Enter Elements [Press -1 to Exit] : 6 5 10 9 7 3 -1
+    Linked List                       : 3 -> 7 -> 9 -> 10 -> 5 -> 6
+
+Case 2: [Input from FILE]  (i.e In Terminal: program_file.cpp < input.txt)
+    Linked List                       : -1 -> 7 -> 19 -> 3 -> 10 -> 9 -> 5 -> 4
+
+*/