added question on Linked List

Linked_List/Detect_cycle_in_LinkedList.cpp

@@ -0,0 +1,91 @@
+
+#include <bits/stdc++.h>
+using namespace std;
+
+struct Node
+{
+    int data;
+    Node* next;
+
+    Node(int val)
+    {
+        data = val;
+        next = NULL;
+    }
+};
+
+void loopHere(Node* head, Node* tail, int position)
+{
+    if(position==0) return;
+
+    Node* walk = head;
+    for(int i=1; i<position; i++)
+        walk = walk->next;
+    tail->next = walk;
+}
+
+
+class Solution
+{
+    public:
+    //Function to check if the linked list has a loop.
+    bool detectLoop(Node* head)
+
+    {
+
+        Node *slow=head,*fast=head;
+
+        while(fast!=NULL && fast->next!=NULL){
+
+            slow=slow->next;
+
+            fast=fast->next->next;
+
+
+
+            if(slow==fast)
+
+                return true;
+
+        }
+
+            return false;
+
+    }
+};
+
+
+
+int main()
+{
+    int t;
+    cin>>t;
+    while(t--)
+    {
+        int n, num;
+        cin>>n;
+
+        Node *head, *tail;
+        cin>> num;
+        head = tail = new Node(num);
+
+        for(int i=0 ; i<n-1 ; i++)
+        {
+            cin>> num;
+            tail->next = new Node(num);
+            tail = tail->next;
+        }
+
+        int pos;
+        cin>> pos;
+        loopHere(head,tail,pos);
+
+        Solution ob;
+        if(ob.detectLoop(head) )
+            cout<< "True\n";
+        else
+            cout<< "False\n";
+    }
+	return 0;
+}
+

Linked_List/Flattening_a_LinkedList.cpp

@@ -0,0 +1,84 @@
+// C++ code for the above approach
+#include <bits/stdc++.h>
+using namespace std;
+
+// Linked list Node
+struct Node {
+	int data;
+	struct Node* next;
+	struct Node* bottom;
+
+	Node(int x)
+	{
+		data = x;
+		next = NULL;
+		bottom = NULL;
+	}
+};
+
+// comparator function for priority queue
+struct mycomp {
+	bool operator()(Node* a, Node* b)
+	{
+		return a->data > b->data;
+	}
+};
+
+void flatten(Node* root)
+{
+	priority_queue<Node*, vector<Node*>, mycomp> p;
+	// pushing main link nodes into priority_queue.
+	while (root != NULL) {
+		p.push(root);
+		root = root->next;
+	}
+
+	// Extracting the minimum node
+	// while priority queue is not empty
+	while (!p.empty()) {
+
+		// extracting min
+		auto k = p.top();
+		p.pop();
+
+		// printing least element
+		cout << k->data << " ";
+		if (k->bottom)
+			p.push(k->bottom);
+	}
+}
+
+// Driver's code
+int main(void)
+{
+	// This code builds the flattened linked list
+	// of first picture in this article ;
+	Node* head = new Node(5);
+	auto temp = head;
+	auto bt = head;
+	bt->bottom = new Node(7);
+	bt->bottom->bottom = new Node(8);
+	bt->bottom->bottom->bottom = new Node(30);
+	temp->next = new Node(10);
+
+	temp = temp->next;
+	bt = temp;
+	bt->bottom = new Node(20);
+	temp->next = new Node(19);
+	temp = temp->next;
+	bt = temp;
+	bt->bottom = new Node(22);
+	bt->bottom->bottom = new Node(50);
+	temp->next = new Node(28);
+	temp = temp->next;
+	bt = temp;
+	bt->bottom = new Node(35);
+	bt->bottom->bottom = new Node(40);
+	bt->bottom->bottom->bottom = new Node(45);
+
+	// Function call
+	flatten(head);
+	cout << endl;
+	return 0;
+}
+// this code is contributed by user_990i

Linked_List/Middle_of_LinkedList.cpp

@@ -0,0 +1,83 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+// Link list node
+struct node
+{
+	int data;
+	struct node* next;
+};
+
+// Function to get the middle of
+// the linked list
+void printMiddle(struct node* head)
+{
+	int count = 0;
+	struct node* mid = head;
+
+	while (head != NULL)
+	{
+
+		// Update mid, when 'count'
+		// is odd number
+		if (count & 1)
+			mid = mid->next;
+
+		++count;
+		head = head->next;
+	}
+
+	// If empty list is provided
+	if (mid != NULL)
+		printf("The middle element is [%d]\n\n",
+				mid->data);
+}
+
+void push(struct node** head_ref, int new_data)
+{
+
+	// Allocate node
+	struct node* new_node = (struct node*)malloc(
+		sizeof(struct node));
+
+	// Put in the data
+	new_node->data = new_data;
+
+	// Link the old list off the new node
+	new_node->next = (*head_ref);
+
+	// Move the head to point to
+	// the new node
+	(*head_ref) = new_node;
+}
+
+// A utility function to print
+// a given linked list
+void printList(struct node* ptr)
+{
+	while (ptr != NULL)
+	{
+		printf("%d->", ptr->data);
+		ptr = ptr->next;
+	}
+	printf("NULL\n");
+}
+
+// Driver code
+int main()
+{
+
+	// Start with the empty list
+	struct node* head = NULL;
+	int i;
+
+	for(i = 5; i > 0; i--)
+	{
+		push(&head, i);
+		printList(head);
+		printMiddle(head);
+	}
+	return 0;
+}
+
+// This code is contributed by ac121102

Linked_List/Nth node from end.cpp

@@ -0,0 +1,89 @@
+//{ Driver Code Starts
+// C program to find n'th Node in linked list
+#include <stdio.h>
+#include <stdlib.h>
+#include<iostream>
+using namespace std;
+
+/* Link list Node */
+struct Node {
+  int data;
+  struct Node *next;
+  Node(int x) {
+    data = x;
+    next = NULL;
+  }
+};
+
+
+/* Function to get the nth node from the last of a linked list*/
+int getNthFromLast(struct Node* head, int n);
+
+
+
+/* Driver program to test above function*/
+int main()
+{
+  int T,i,n,l,k;
+
+    cin>>T;
+
+    while(T--){
+    struct Node *head = NULL,  *tail = NULL;
+
+        cin>>n>>k;
+        int firstdata;
+        cin>>firstdata;
+        head = new Node(firstdata);
+        tail = head;
+        for(i=1;i<n;i++)
+        {
+            cin>>l;
+            tail->next = new Node(l);
+            tail = tail->next;
+        }
+
+    cout<<getNthFromLast(head, k)<<endl;
+    }
+    return 0;
+}
+// } Driver Code Ends
+
+
+/* struct Node {
+  int data;
+  struct Node *next;
+  Node(int x) {
+    data = x;
+    next = NULL;
+  }
+};
+*/
+
+//Function to find the data of nth node from the end of a linked list.
+int getNthFromLast(Node *head, int n)
+
+{
+
+    int cnt=0;
+
+    Node* temp=head;
+
+    while(head){
+
+        head=head->next;
+
+        cnt++;
+
+    }
+
+    if(cnt<n) return -1;
+
+    cnt=cnt-n;
+
+    while(cnt--)temp=temp->next;
+
+    return temp->data;
+
+}
+