Detect Loop in Linked List

Java8Features/JavaEight.java

@@ -0,0 +1,103 @@
+import java.util.*;
+import java.util.function.Predicate;
+import java.util.function.BiPredicate;
+import java.util.function.Function;
+import java.util.function.BiFunction;
+import java.util.function.Consumer;
+import java.util.function.BiConsumer;
+import java.util.function.Supplier;
+import java.util.function.IntFunction;
+import java.util.function.IntUnaryOperator;
+import java.util.function.BinaryOperator;
+
+interface TestInterf{
+public void sumofvar(int a,int b);
+}
+interface NewInterf{
+public int getlen(String s);
+}
+interface Fun{
+public String convert(String s);
+}
+
+class JavaEight{
+public static void main(String []args)
+{
+/*TestInterf sum = (a,b) -> System.out.println(a+b);
+sum.sumofvar(3,4);
+
+NewInterf obj = (s) -> s.length();
+System.out.println(obj.getlen("naman"));
+
+Fun obj2 = (s) -> s.toUpperCase();
+System.out.println(obj2.convert("naman"));
+
+
+Runnable r = () -> {
+for(int i=0;i<10;i++)
+{
+System.out.println("child thread "+i);
+}
+};
+Thread t = new Thread(r);
+t.start();
+for(int i=0;i<10;i++)
+{
+System.out.println("main thread"+i);
+}
+
+
+Predicate<String> pred = s -> s.length() > 10;
+System.out.println(pred.test("asdc"));
+
+BiPredicate<Integer,Integer> pred1 = (a,b)-> (a+b)>10;
+System.out.println(pred1.test(12,5));
+
+
+
+Function<Integer,Integer> fun = a -> a*a;
+System.out.println(fun.apply(3));
+
+BiFunction<String,String,Integer> func1 = (a,b) -> (a+b).length();
+System.out.println(func1.apply("Hi ","trainees!"));
+
+Function<String,String> f1 = s -> s.toUpperCase();
+Function<String,String> f2 = s -> s.substring(0,2);
+System.out.println(f1.andThen(f2).apply("tata"));
+System.out.println(f1.compose(f2).apply("training session"));
+
+
+Function<Integer,Integer> f3 = i -> i-2;
+Function<Integer,Integer> f4 = i -> i*4;
+System.out.println(f3.compose(f4).apply(3)); 
+
+Function<Integer,Integer> f5 = i -> i*4;
+Function<Integer,Integer> f6 = i -> i-2;
+System.out.println(f5.compose(f6).apply(3)); 
+
+
+Consumer<Double> con = a -> System.out.println(a/7);
+con.accept(50.0);
+BiConsumer<String,String> con1 = (a,b) -> System.out.println(a+b);
+con1.accept("Naman","Khurpia"); 
+
+
+Supplier<Date> s = () -> new Date();
+System.out.println(s.get());
+
+
+
+IntFunction<Integer> fun = a -> a*a;
+System.out.println(fun.apply(25));
+
+
+IntUnaryOperator uo = a -> a+10;
+System.out.println(uo.applyAsInt(40));
+
+*/
+
+BinaryOperator<String> binary = (a,b) -> a+b;
+System.out.println(binary.apply("Fri"+"day"));
+
+}
+}

README.md

@@ -1,14 +1,14 @@
-# DS-Algo
-Implementation of Data structures and Algorithms at Apni Kaksha Java Placement Course.
+# Data Structures-Algorithms
+Implementation of Data structures and Algorithms at Apni Kaksha Java Placement Course.It covers all the important Data structures and Algorithms and also coding problems which are really important from the interview point of view.
+<br>Anuj Bhaiya is the creator of this course.If you have any kind of doubts,you may reach him out:<a href="https://www.instagram.com/anuj.kumar.sharma/"></i>Anuj Kumar Sharma</a>
 <br>
 <h3>Installation</h3>
 <ul>
   <li><a href="https://www.oracle.com/java/technologies/javase-downloads.html"> JDK - Download</a></li>
   <li><a href="https://www.eclipse.org/downloads/"> Eclipse IDE - Download </a></li>
 </ul>
-
 <br>
-<h3>Topic Covered</h3>
+<h3><u>Topics Covered:</u></h3>
 <ul>
   <li><a href="https://www.youtube.com/watch?v=A05CDzFJ010&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s&index=44&t=0s">Vector</a></li>
   <li><a href ="https://www.youtube.com/watch?v=A05CDzFJ010&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s&index=44&t=0s">Stacks</a></li>
@@ -18,9 +18,11 @@ Implementation of Data structures and Algorithms at Apni Kaksha Java Placement C
   <li><a href ="https://www.youtube.com/watch?v=APSx9uzhz6o&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s&index=52&t=0s">Maps</a></li>
   <li><a href ="https://www.youtube.com/watch?v=pXk_0RX_d7c&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s&index=40&t=0s">Lists</a></li>
   <li><a href ="https://www.youtube.com/watch?v=6KKIZL1wt8o&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s&index=43&t=0s">Linked List</a></li>
-  <li><a href ="https://www.youtube.com/watch?v=XDJKHtXJHBY&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s&index=49&t=0s">Interview Questions</a></li>
+  <li><a href ="https://www.youtube.com/watch?v=XDJKHtXJHBY&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s&index=49&t=0s">Important Interview Questions</a></li>
   <li><a href ="https://www.youtube.com/watch?v=zSX7N5MolB8&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s&index=36&t=0s">Interfaces</a></li>
   <li><a href ="https://www.youtube.com/watch?v=V_NVMqxcNaI&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s&index=47&t=0s">Doubly Ended Queue</a></li>
 </ul>
 <br>
-<h3>YouTube Playlist (Video tutorial)- <a href ="https://www.youtube.com/watch?v=lxja8wBwN0k&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s">Java Data Structures and Algorithm</a></h3>
+
+<h3>YouTube Playlist: <a href ="https://www.youtube.com/watch?v=lxja8wBwN0k&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s">Java ,Data Structures and Algorithms</a></h3>
+<h3> All about Git and Github:<a href ="https://www.youtube.com/watch?v=iR5WIknxdkY&list=PLKKfKV1b9e8ps6dD3QA5KFfHdiWj9cB1s&index=41&t=2406s">Git and Github</a></h3>

deque/MainClass.java

@@ -8,9 +8,13 @@ public static void main(String[] args) {
 
 		ArrayDeque<Integer> ad = new ArrayDeque<>();
 
+
+		//push method to push the element in the array double ended queue
 		ad.push(12);
 		ad.push(23);
 		ad.push(34);
+
+		//pop method to pop the element at the beginning of a array double ended queue
 
 		System.out.println(ad.pop());
 		System.out.println(ad.pop());

interviewQuestions/DetectLoop.java

@@ -0,0 +1,69 @@
+import java.util.*;
+import java.io.*;
+
+
+class Node
+{
+    int data;
+    Node next;
+
+    Node(int x)
+    {
+        data = x;
+        next = null;
+    }
+}
+
+class LinkedList
+{  
+    public static void main (String[] args)
+    {
+        Scanner sc = new Scanner(System.in);
+        int t = sc.nextInt();
+
+        while(t--> 0)
+        {
+            int n = sc.nextInt();
+
+            int key = sc.nextInt();
+            Node head= new Node(key);
+            Node tail= head;
+
+            for(int i=0;i<n-1;i++)
+            {
+                key = sc.nextInt();
+                tail.next = new Node(key);
+                tail = tail.next;
+            } 
+
+	//for testing,we can create a loop by inserting the next line
+		//head.next= head 
+          //loops can be created in several ways
+
+            if(detectLoop(head))
+                System.out.println("True");
+            else
+                System.out.println("False");
+        }
+    }
+    public static boolean detectLoop(Node head)
+    {
+        Node fast=head;
+        Node slow=head;
+
+       while (slow!= null && fast!= null && fast.next!=null) 
+        { 
+            slow=slow.next; 
+            fast=fast.next.next; 
+            if(slow==fast)  
+            { 	// there exists a loop if and only if both fast and slow pointer point to a same one during traversal
+                return true;
+            } 
+        } 
+
+        return false;
+    }
+}
+
+
+

interviewQuestions/DetectLoop1.java

@@ -0,0 +1,69 @@
+import java.util.*;
+import java.io.*;
+
+
+class Node
+{
+    int data;
+    Node next;
+
+    Node(int x)
+    {
+        data = x;
+        next = null;
+    }
+}
+
+class LinkedList
+{  
+    public static void main (String[] args)
+    {
+        Scanner sc = new Scanner(System.in);
+        int t = sc.nextInt();
+
+        while(t--> 0)
+        {
+            int n = sc.nextInt();
+
+            int key = sc.nextInt();
+            Node head= new Node(key);
+            Node tail= head;
+
+            for(int i=0;i<n-1;i++)
+            {
+                key = sc.nextInt();
+                tail.next = new Node(key);
+                tail = tail.next;
+            } 
+
+	//for testing,we can create a loop by inserting the next line
+		//head.next= head 
+          //loops can be created in several ways
+
+            if(detectLoop(head))
+                System.out.println("True");
+            else
+                System.out.println("False");
+        }
+    }
+    public static boolean detectLoop(Node head)
+    {
+        Node fast=head;
+        Node slow=head;
+
+       while (slow!= null && fast!= null && fast.next!=null) 
+        { 
+            slow=slow.next; 
+            fast=fast.next.next; 
+            if(slow==fast)  
+            { 	// there exists a loop if and only if both fast and slow pointer point to a same one during traversal
+                return true;
+            } 
+        } 
+
+        return false;
+    }
+}
+
+
+

interviewQuestions/HeightCheckerLeetcode.java

@@ -0,0 +1,16 @@
+class Solution {
+      public int heightChecker(int[] heights) {
+        int[] countArr = new int[101];
+        for(int h:heights){
+            countArr[h]++;
+        }
+        int res=0;
+        int curr =0;
+        for(int h:heights){
+            while(countArr[curr]==0)curr++;
+            if(h != curr) res++;
+            countArr[curr]--;
+        }
+        return res;
+    }
+}

interviewQuestions/SubarrayWithZeroSum.java

@@ -32,6 +32,8 @@ public static void main(String[] args) {
 		for (int element : a) {
 			set.add(sum);
 			sum += element;
+      //Zero sum will only exist if the cumulative sum of the elements excluding the current element
+      //and after including the current element are equal
 			if (set.contains(sum - k)) {
 				found = true;
 				break;

linkedLists/MainLinkedList.java

@@ -8,11 +8,15 @@ public static void main(String[] args) {
 
 		MyLinkedList<String> myLL = new MyLinkedList();
 
+
 		for (int i = 0; i < 10; i++) {
-			myLL.add(i + "added");
-		}
+			// add method use to add a element in the last node of the linked list
+      myLL.add(i + "added");
 
+		}
+// print method use to print the linked list
 		myLL.print();
 	}
 
 }
+

linkedLists/MyLinkedList.java

@@ -2,6 +2,8 @@
 
 public class MyLinkedList<E> {
 
+
+//E is the Class defining the type of the inputs accepted
 	Node<E> head;
 
 	public void add(E data) {
@@ -12,10 +14,14 @@ public void add(E data) {
 			return;
 		}
 
+//initialising temp as head to traverse the Linked list without breaking the chain
 		Node<E> temp = head;
+      // control from loop exits as soon as next element becomes null
 		while (temp.next != null) {
+
 			temp = temp.next;
 		}
+    // adding the new node after reaching to the end of linked list
 		temp.next = toAdd;
 	}
 
@@ -48,7 +54,7 @@ public E removeLast() throws Exception {
 			temp = temp.next;
 		}
 		Node<E> toRemove = temp.next;
-		temp.next = null;
+		temp.next = null; // changing the pointer of temp.next from toRemove to null,and garbage collection is done automatically
 		return toRemove.data;
 	}
 
@@ -68,7 +74,9 @@ public static class Node<E> {
 		public E data;
 		public Node<E> next;
 
+//constructor
 		public Node(E data) {
+
 			this.data = data;
 			next = null;
 		}

lists/MyArrayList.java

@@ -9,7 +9,8 @@ public class MyArrayList {
 	public static void main(String[] args) {
 
 		List<String> fruits = new LinkedList();
-
+
+		//method to add the element in the list
 		fruits.add("Apple");
 		fruits.add("Orange");
 		fruits.add("Hi");