Added Arrays and Strings in array folder and linked list questions in linked list folder (#255)

* Added arrays and strings

* added 500+ linked list questions in linked list folder

Author: AbhishekCS3459

CPP/LINKED LIST/ALGORITHMIC PROBLEMS RELATED TO LINKEDLIST/.cph/.detectloop.cpp_2abfa101b0e3a24a4a7eb18c37e1f6b7.prob

@@ -0,0 +1 @@
+{"name":"Local: detectloop","url":"d:\\DSA-COMPETITIVE-CODING-master\\WEEK-4\\Lecture-47\\detectloop.cpp","tests":[],"interactive":false,"memoryLimit":1024,"timeLimit":3000,"srcPath":"d:\\DSA-COMPETITIVE-CODING-master\\WEEK-4\\Lecture-47\\detectloop.cpp","group":"local","local":true}

CPP/LINKED LIST/ALGORITHMIC PROBLEMS RELATED TO LINKEDLIST/.cph/.test4.cpp_90c85920d1f8edf138432e724faefbe1.prob

@@ -0,0 +1 @@
+{"name":"Local: test4","url":"d:\\DSA-COMPETITIVE-CODING-master\\WEEK-4\\Lecture-47\\test4.cpp","tests":[{"id":1662390825919,"input":"5","output":""}],"interactive":false,"memoryLimit":1024,"timeLimit":3000,"srcPath":"d:\\DSA-COMPETITIVE-CODING-master\\WEEK-4\\Lecture-47\\test4.cpp","group":"local","local":true}

CPP/LINKED LIST/ALGORITHMIC PROBLEMS RELATED TO LINKEDLIST/.cph/.test5.cpp_eb24249193dd48e5ca6990414caf7598.prob

@@ -0,0 +1 @@
+{"name":"Local: test5","url":"d:\\DSA-COMPETITIVE-CODING-master\\WEEK-4\\Lecture-47\\test5.cpp","tests":[{"id":1662461248249,"input":"this is level 71","output":""}],"interactive":false,"memoryLimit":1024,"timeLimit":3000,"srcPath":"d:\\DSA-COMPETITIVE-CODING-master\\WEEK-4\\Lecture-47\\test5.cpp","group":"local","local":true}

CPP/LINKED LIST/ALGORITHMIC PROBLEMS RELATED TO LINKEDLIST/.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+    "files.associations": {
+        "iostream": "cpp"
+    }
+}

CPP/LINKED LIST/ALGORITHMIC PROBLEMS RELATED TO LINKEDLIST/detectloop.cpp

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+// Love Babbar Reverse K linked List .
+// leet code-25
+// Microsoft Interview 
+
+
+
+#include<bits/stdc++.h>
+using namespace std;
+#define ll long long
+#define fi(a,n) for(int i=a;i<n;i++)
+class node{
+    public:
+    int data;
+    node*next;
+    node(int data){
+        this->data=data;
+        this->next=NULL;
+    }
+};
+
+
+void print(node*&head){
+    node*temp=head;
+    while (temp!=NULL)
+    {
+        cout<<temp->data<<" ";
+        temp=temp->next;
+ 
+    }
+    cout<<endl;
+}
+void insertathead(node*&head,int data){
+    node*nodetoinsert=new node(data);
+    nodetoinsert->next=head;
+    head=nodetoinsert;
+}
+void insertattail(node*&tail,int data){
+    node*nodetoinsert=new node(data);
+    tail->next=nodetoinsert;
+    tail=nodetoinsert;
+}
+void insertatposition(node*head,node*&tail,int data,int position){
+    // if the list is empty
+    if(head==NULL){
+        insertathead(head,data);
+        return;
+    }
+    int ct=1;
+    node*temp=head;
+    while (ct<=position-1)
+    {
+        temp=temp->next;
+        ct++;
+    }
+    if(temp->next=NULL){
+        insertattail(tail,data);
+        return;
+    }
+   node*nodetoinsert=new node(data);
+   nodetoinsert->next=temp->next;
+   temp->next=nodetoinsert;
+
+    
+}
+int detectcycle(node*&head){
+    map<node*,bool>m;
+  node*temp=head;
+  while (temp!=NULL)
+  {
+    if(m[temp]==true)
+    return 1;
+    // if it is circular
+      m[temp]=true;
+      temp=temp->next;
+     
+  }
+   return 0;
+}
+int main(){
+ ios_base::sync_with_stdio(false);
+  cin.tie(NULL);
+
+ node *n1=new node(5);
+
+  node*head=n1;
+  node*tail=n1;
+
+  insertathead(head,4);
+  insertathead(head,3);
+  insertathead(head,2);
+  insertathead(head,1);
+  insertattail(tail,6);
+   print(head);
+  tail->next=head->next->next;
+  cout<< detectcycle(head)<<endl;
+  
+  
+return 0;
+}
+

CPP/LINKED LIST/ALGORITHMIC PROBLEMS RELATED TO LINKEDLIST/detectloop.exe

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+// Love Babbar Reverse K linked List .
+// leet code-25
+// Microsoft Interview 
+
+
+
+#include<bits/stdc++.h>
+using namespace std;
+#define ll long long
+#define fi(a,n) for(int i=a;i<n;i++)
+class node{
+    public:
+    int data;
+    node*next;
+    node(int data){
+        this->data=data;
+        this->next=NULL;
+    }
+   
+};
+
+
+void print(node*&head){
+    node*temp=head;
+    while (temp!=NULL)
+    {
+        cout<<temp->data<<" ";
+        temp=temp->next;
+ 
+    }
+    cout<<endl;
+}
+void insertathead(node*&head,int data){
+    node*nodetoinsert=new node(data);
+    nodetoinsert->next=head;
+    head=nodetoinsert;
+}
+void insertattail(node*&tail,int data){
+    node*nodetoinsert=new node(data);
+    tail->next=nodetoinsert;
+    tail=nodetoinsert;
+}
+void insertatposition(node*head,node*&tail,int data,int position){
+    // if the list is empty
+    if(head==NULL){
+        insertathead(head,data);
+        return;
+    }
+    int ct=1;
+    node*temp=head;
+    while (ct<=position-1)
+    {
+        temp=temp->next;
+        ct++;
+    }
+    if(temp->next=NULL){
+        insertattail(tail,data);
+        return;
+    }
+   node*nodetoinsert=new node(data);
+   nodetoinsert->next=temp->next;
+   temp->next=nodetoinsert;
+
+    
+}
+node* floyd_cycle(node*&head){
+if(head==NULL)
+return NULL;
+node*slow=head;
+node*fast=head;
+node*temp=head;
+while (slow!=NULL&& fast!=NULL)
+{
+    fast=fast->next;
+    if(fast!=NULL){
+        fast=fast->next;
+    }
+    slow=slow->next;
+    if(slow==fast)
+    {
+        return slow;
+    }
+}
+return NULL;
+
+}
+node*get_starting_node(node*head){
+    if(head==NULL){
+        return NULL;
+    }
+    node*low=head;
+    node*get_intersection=floyd_cycle(head);
+    
+    while (low!=get_intersection)
+    {
+        low=low->next;
+        get_intersection=get_intersection->next;
+        
+    }
+    
+    return low;
+}
+
+node*remove_circle(node*head){
+    if(head==NULL)return NULL;
+    node*low=get_starting_node(head);
+    node*fast=get_starting_node(head);
+    while (fast->next!=low)
+    {
+        fast=fast->next;
+    }
+    fast->next=NULL;
+    return head;
+    
+}
+
+int detectcycle(node*&head){
+    if(head==NULL){
+        return false;
+    }
+    map<node*,bool>m;
+  node*temp=head;
+  while (temp!=NULL)
+  {
+    if(m[temp]==true)
+    return 1;
+    // if it is circular
+      m[temp]=true;
+      temp=temp->next;
+     
+  }
+   return 0;
+}
+int main(){
+ ios_base::sync_with_stdio(false);
+  cin.tie(NULL);
+
+ node *n1=new node(5);
+
+  node*head=n1;
+  node*tail=n1;
+
+  insertathead(head,4);
+  insertathead(head,3);
+  insertathead(head,2);
+  insertathead(head,1);
+  insertattail(tail,6);
+   print(head);
+  tail->next=head->next->next;
+  cout<< detectcycle(head)<<endl;
+  cout<<endl;
+
+// if(floyd_cycle(head)){
+//     cout<<"cycle is present "<<endl;
+// }  
+// else
+// cout<<"Cycle is not present"<<endl; 
+  node*ans=get_starting_node(head);
+  cout<<ans->data<<" ";
+  node*ans2=remove_circle(head);
+  cout<<endl;
+  print(ans2);
+return 0;
+}
+