From 364e4895543c6fbf9670b0a45c8777ff31247fe0 Mon Sep 17 00:00:00 2001
From: Sundeep Chand <sundeep.chand2001@gmail.com>
Date: Sat, 5 Oct 2019 15:30:20 +0530
Subject: [PATCH] Added Linked List

---
 Data Structures/LinkedList/LinkedList.cpp | 173 ++++++++++++++++++++++
 1 file changed, 173 insertions(+)
 create mode 100644 Data Structures/LinkedList/LinkedList.cpp

diff --git a/Data Structures/LinkedList/LinkedList.cpp b/Data Structures/LinkedList/LinkedList.cpp
new file mode 100644
index 0000000..3b6e77f
--- /dev/null
+++ b/Data Structures/LinkedList/LinkedList.cpp	
@@ -0,0 +1,173 @@
+/*
+Program to implement linked list.
+*/
+#include <iostream>
+using namespace std;
+
+//Define a structure for node.
+struct Node {
+    int data;
+    Node* next;
+};
+
+Node* head = NULL; // empty list
+
+//Functions to operate on the list.
+void Insert(int value) {
+    ///Function to inset a node at the beginning of the list.
+    Node* temp = new Node;
+    temp->data = value;
+    temp->next = head;
+    head = temp;
+}
+
+void Insert(int value, int pos) {
+    ///Inserts a node at the n th position (1 based indexing).
+    Node* new_node = new Node;
+    new_node->data = value;
+
+    if (pos == 1) {
+        new_node->next = head;
+        head = new_node;
+        return;
+    }
+
+    Node* temp = head;
+    for (int i = 0; i < pos-2 && temp != NULL; i++) {
+        temp = temp->next;
+        //cout<<"Currently at node "<<i<<endl;
+    }
+    if (temp != NULL) {
+        new_node->next = temp->next;
+        temp->next = new_node;
+    }
+    else {
+        cout<<"Position out of bounds."<<endl;
+    }
+}
+
+void Append(int value) {
+    ///Function to insert the node at the end of the list.
+    Node* new_node = new Node;
+    new_node->data = value;
+
+    if (head == NULL) {
+        new_node->next = head;
+        head = new_node;
+        return;
+    }
+    // Go to the end of the list.
+    Node* temp = head;
+    while (temp->next != NULL) {
+        temp = temp->next;
+    }
+    new_node->next = NULL;
+    temp->next = new_node;
+}
+
+void Delete(int pos) {
+    ///Function to delete the node at n th position (1 based indexing).
+    Node* temp, *prev_node = head;
+
+    if (pos == 1) {
+        temp = head;
+        head = head->next;
+        delete temp;
+        return;
+    }
+
+    for (int i = 0; i < pos-2 && prev_node != NULL; i++) {
+        prev_node = prev_node->next;
+    }
+
+    if (prev_node == NULL || prev_node->next == NULL || pos <= 0) {
+        cout<<"Entered index out of bounds."<<endl;
+        return;
+    }
+    temp = prev_node->next;
+    prev_node->next = temp->next;
+    delete temp;
+}
+
+void Print() {
+    ///Function to traverse the list & print it.
+    Node* temp = head;
+    cout<<"List is: ";
+    while (temp != NULL) {
+        cout<<temp->data<<" -> ";
+        temp = temp->next;
+    }
+    cout<<"NULL"<<endl;
+}
+
+void Print_recursive(Node* current) {
+    cout<<current->data<<" -> ";
+    if (current->next != NULL)
+        Print_recursive(current->next);
+}
+
+void Print_recursive_reverse(Node* current) {
+    if (current->next != NULL)
+        Print_recursive_reverse(current->next);
+    cout<<current->data<<" -> ";
+}
+
+void Reverse() {
+    Node *current, *prev, *next;
+    current = head;
+    prev = NULL;
+    while (current != NULL) {
+        next = current->next;
+        current->next = prev;
+        prev = current;
+        current = next;
+    }
+    head = prev;
+}
+
+void Reverse_recursive(Node *current){
+    if (current->next == NULL) {
+        head = current;
+        return;
+    }
+    Reverse_recursive(current->next);
+    current->next->next = current;
+    current->next = NULL;
+}
+
+void Clear_heap() {
+    ///Function to clear the allocated memory.
+    Node* temp = head;
+    while (temp != NULL) {
+        head = head->next;
+        delete temp;
+        temp = head;
+    }
+}
+
+int main() {
+    head = NULL; //empty list.
+
+    //Create the list.
+    Append(2);
+    Append(4);
+    Append(6);
+    Append(5);
+    Append(7);
+
+    Print_recursive(head);      // HEAD -> 2 -> 4 -> 6 -> 5 -> 7 -> NULL
+    cout<<endl;
+    //Print_recursive_reverse(head);
+    Reverse_recursive(head);
+    Print();
+
+    /*
+    int pos;
+    cout<<"Enter the position from where you want to delete: ";
+    cin>>pos;
+    Delete(pos);
+    */
+
+    Clear_heap(); // Clear the list.
+    return 0;
+}