From 85f40630cbfaa9035ac8984c76ce935f7ffbc116 Mon Sep 17 00:00:00 2001
From: Ashish kumar <49323368+ashishkumar295@users.noreply.github.com>
Date: Fri, 7 Feb 2020 17:44:36 +0530
Subject: [PATCH] Create linked list.cpp

---
 linked list.cpp | 211 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 211 insertions(+)
 create mode 100644 linked list.cpp

diff --git a/linked list.cpp b/linked list.cpp
new file mode 100644
index 0000000..487a7a9
--- /dev/null
+++ b/linked list.cpp	
@@ -0,0 +1,211 @@
+#include <bits/stdc++.h>
+using namespace std;
+struct Node{
+    int data;
+    Node *next;
+};
+
+//INSERTION IN SINGLY LINKED LIST 
+
+void push(Node** head_ref,int data)//insertion at front
+{
+    Node* newnode=new Node;
+    newnode->data=data;
+    newnode->next=*head_ref;
+    *head_ref=newnode;
+}
+
+
+void append(Node **head_ref,int data)//insertion at the end
+{
+    Node *newnode=new Node;
+    newnode->data=data;
+    newnode->next=NULL;
+    Node *last=*head_ref;
+    if(*head_ref==NULL)//check if list is empty
+    {
+        *head_ref=newnode;
+        return;
+        
+    }
+    
+    while(last->next!=NULL)
+    last=last->next;
+    last->next=newnode;
+}
+
+
+//DELETION OF NODE  IN SINGLY LINKED LIST
+
+//Deleting node at the beginning of the linked list
+void popfront(Node** head_ref)
+{
+	Node *temp=*head_ref;
+	if(*head_ref==NULL)
+	{
+		cout<<"List empty\n";
+		return;
+	}
+	*head_ref=temp->next;
+	free(temp);
+	
+	
+}
+//Deleting the node from  the end 
+ void popback(Node** head)
+ {
+     Node *p=*head;
+     if(*head==NULL )
+     {
+         cout<<"List empty\n";
+         return;
+     }
+     else if (p->next==NULL)
+     {
+         Node *temp=*head;
+         *head=NULL;
+         free(temp);
+     }
+     else
+     {
+         
+         Node *temp=p->next;
+         while(temp->next!=NULL)
+         {
+             p=temp;
+             temp=temp->next;
+         }
+         p->next=NULL;
+         free(temp);
+     }
+ }
+
+
+
+//Deleting node with  the given key
+void delkey(Node**head_ref,int key)
+{
+    Node *temp=*head_ref,*prev;
+    if(temp!=NULL and temp->data==key)
+    {
+        *head_ref=temp->next;
+        free(temp);
+        return;
+    }
+    while(temp!=NULL and temp->data!=key)
+    {
+        prev=temp;
+        temp=temp->next;
+    }
+    if(temp==NULL)
+    return;
+    prev->next=temp->next;
+    free(temp);
+}
+
+//Deletion of linked list
+
+void deletelist(Node**head)
+{
+    Node* next,*current=*head;
+    while(current!=NULL)
+    {
+        next=current->next;
+        free(current);
+        current=next;
+    }
+    *head=NULL;
+}
+
+//Display the Linked list
+void display(Node *head)
+{
+    if(head==NULL)
+    {
+        cout<<"Empty List\n";
+        return;
+    }
+    while(head!=NULL)
+    {
+        cout<<head->data<<" ";
+        head=head->next;
+    }
+    cout<<endl;
+}
+
+
+//Detect loop in linked list method 1:Hashing
+bool detectloop1(Node* h)
+{
+    unordered_set<Node*> s;
+    while(h!=NULL)
+    {
+        if(s.find(h)!=s.end())
+        return true;
+        s.insert(h);
+        h=h->next;
+        
+    }
+    return false;
+}
+//Detect loop in in a linked list using floyd cycle detection
+
+bool detectloop2(Node *h)
+{
+    Node *s=h,*f=h;
+    while(s and f and f->next)
+    {
+        s=s->next;
+        f=f->next->next;
+        if(s==f)
+        return true;
+    }
+    return false;
+}
+
+//reverse a linked list
+void reverse(Node**head)
+{
+    Node *curr=*head;
+    Node *prev=NULL,*next=NULL;
+    while(curr!=NULL)
+    {
+        next=curr->next;
+        curr->next=prev;
+        prev=curr;
+        curr=next;
+    }
+    *head=prev;
+}
+
+
+
+
+int main()
+{
+    Node *head=NULL;
+    push(&head,10);
+    append(&head,20);
+    append(&head,30);
+    append(&head,40);
+    push(&head,5);
+    push(&head,1);
+    display(head);
+    popback(&head);
+   // head->next->next->next=head;
+    // deletelist(&head);
+    
+   // reverse(&head);
+    if(detectloop2(head))
+    {
+    cout<<"LOOP DETECTED\n";
+    
+    }
+    else
+    {
+    cout<<"NO LOOP\n";
+    display(head);
+    }
+    
+    
+}