Linked List basics

java_programs/Linked List/Circular LL Traversal.java

@@ -0,0 +1,31 @@
+public class _26 {
+    static class node{
+        int data;
+        node next;
+        node(int x)
+        {
+            data=x;
+        }
+    }
+    static void Traversal(node head)
+    {
+        if(head==null)
+        return;
+        node curr=head;
+        do{
+            System.out.print(head.data+"    ");
+            head=head.next;
+        }while(head!=curr);
+    }
+    public static void main(String[] args) {
+        node head=new node(10);
+        node temp1=new node(20);
+        node temp2=new node(30);
+        node temp3=new node(40);
+        head.next=temp1;
+        temp1.next=temp2;
+        temp2.next=temp3; 
+        temp3.next=head;
+        Traversal(head);
+    }
+}

java_programs/Linked List/Circular LL.java

@@ -0,0 +1,101 @@
+import java.util.*;
+public class _22 {
+    static class node{
+        int data;
+        node next;
+        node(int x)
+        {
+            data=x;
+        }
+    }
+    static node Insert(node head, int pos, int x)
+    {
+        node curr=new node(x);
+        if(head==null)
+        { curr.next=curr;
+        return curr;
+        }
+        int c=0;
+        if(head.next==null)
+        {
+            head.next=curr;
+            curr.next=head;
+            return head;
+        }
+        pos-=2; //This was done when doing.........
+        node temp=null;
+        node copy=head.next,copy1=head;
+        while(copy!=copy1)
+        {
+            c++;
+            if(pos==c)
+            {
+                temp=copy.next;
+                copy.next=curr;
+                curr.next=temp;
+                break;
+            }
+            copy=copy.next;
+        }
+        return head;
+
+    }
+    static void printList(node head)
+    {
+        System.out.println(head.data+"      ");
+        if(head.next==null)
+        {
+        }
+        else{
+
+        node curr=head;
+        boolean od=true;
+        while(head!=curr || od)
+        {
+            od=false;
+            System.out.print(head.data+"        ");
+            head=head.next;
+        }
+    }
+    }
+    public static void main(String[] args) {
+        Scanner sc=new Scanner(System.in);
+        System.out.println("Enter number of elements you want to print.");
+        int n=sc.nextInt();
+        node head=null;
+        int m=0;
+        for(int i=0;i<n;i++)
+        {
+            if(i==0)
+            {
+                System.out.println("Enter first element");
+            int x=sc.nextInt();
+            head=Insert(head, 1, x);
+            printList(head);
+            m++;
+            }
+            else
+            {
+                System.out.println();
+                System.out.println("Enter element");
+                int x=sc.nextInt();
+                System.out.println("Enter position");
+                int pos=sc.nextInt();
+               if(pos>m+1 ||pos<0)
+               {
+                System.out.println("The position you entered is incorrect.");
+                i--;
+               }
+               else{
+                head=Insert(head, pos, x);
+                printList(head);
+                m++;
+               }
+
+            }
+
+        }
+        // System.out.println();
+        // System.out.println(head.data+"   "+head.next.data+"    "+head.next.next.data+"     "+head.next.next.next.data);
+    }
+}

java_programs/Linked List/Delete first node of singly LL.java

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+
+public class _10 {
+    static class node{
+        int data;
+        node next;
+        node(int x)
+        {
+            data=x;
+        }
+    }
+    static void printList(node head)
+    {
+        while(head!=null)
+        {
+            System.out.println(head.data);
+            head=head.next;
+        }
+    }
+    static node DeleteFirst(node head)
+    {
+        if(head==null)
+        System.exit(0);
+        else
+        head=head.next;
+        return head;
+
+    }
+    public static void main(String[] args) {
+        node head=new node(0);
+        head.next=new node(10);
+        head.next.next=new node(20);
+        head.next.next.next=new node(30);
+        printList(head);
+        // head=head.next;
+        System.out.println();
+        // printList(head);
+        head=DeleteFirst(head);
+        printList(head);
+    }
+}

java_programs/Linked List/Delete head of circular LL.java

@@ -0,0 +1,170 @@
+import java.util.*;
+public class _29 {
+    static class node{
+        int data; 
+        node next;
+        node(int x)
+        {
+            data=x;
+        }
+    }
+    static node Insert(node head, int x, int pos)
+    {
+        node temp=new node(x);
+        if(head==null)
+        {
+            temp.next=temp;
+            return temp;
+        }
+        else if(pos==1)
+        {
+            temp.next=head.next;
+            head.next=temp;
+            int t=head.data;
+            head.data=temp.data;
+            temp.data=t;
+            return head;
+        }
+        else 
+        {
+            node curr=head;
+            int c=2;
+            boolean p=true;
+            while(curr!=head || p)
+            {
+                p=false;
+                if(pos==c)
+                {
+                    temp.next=curr.next;
+                    curr.next=temp;
+                    break;
+                }
+                curr=curr.next;c++;
+            }
+            return head;
+        }
+    }
+    static node Delete(node head, int pos)
+    {
+        if(head.next==head)
+        return null;
+        else{
+            node curr=head;
+            int c=2;
+            while(curr.next!=head)
+            {
+                if(pos==c)
+                {
+                    curr.next=curr.next.next;
+                    break;
+                }
+                c++;
+                curr=curr.next;
+            }
+            if(pos==1)
+            {
+                curr.next=curr.next.next;
+                return curr.next;
+            }
+            else return head;
+        }
+    }
+    static node reverse(node head)
+    {
+        node temp1=head.next, prev=null;
+        while(temp1!=null)
+        {
+            head.next=prev;
+            prev=head;
+            head=temp1;
+            temp1=temp1.next;
+            printList(head);
+        }
+        System.out.println(prev.data);
+        head.next=prev;
+        return head;
+    }
+    static void printList(node head)
+    {
+        node curr=head;
+        while(curr.next!=head)
+        {
+            System.out.print(curr.data+"  ");
+            curr=curr.next;
+        }
+        System.out.println(curr.data);
+
+    }
+public static void main(String[] args) {
+    Scanner sc=new Scanner(System.in);
+    node head=null;
+    System.out.println("If you want to delete elements, enter 'D'.\nIf you want to enter elements, enter 'E'");
+System.out.println("Since this is your first input, 'E' is selected by default");
+char ch='E';
+int x,pos=1,c=0;
+do{
+    if(ch=='E')
+    {
+    do{
+        if(c==0)
+        {
+            System.out.println("Please enter an element. Also, if you want to stop inserting, press '-1' as input;");
+             x=sc.nextInt();
+            head=Insert(head,x, pos);
+            c++;
+            printList(head);
+        }
+        else
+        {
+            System.out.println();
+            System.out.println("Enter element.");
+            x=sc.nextInt();
+            if(x==-1)
+            break;
+            System.out.println("Enter position");
+            pos=sc.nextInt();
+            if(pos>c +1 || pos<1)
+            System.out.println("The position you entered is INCORRECT. Please re-enter.");
+            c++;
+            Insert(head, x, pos);
+            printList(head);
+        }
+    }while(x!=-1);
+        System.out.println("Do you wish to delete some elements. If yes, press 'D'. To exit, press 'F'");
+        ch=sc.next().charAt(0);
+}
+if(ch=='D')
+{
+    do{
+        System.out.println("Enter the position from where you want to delete element");
+        pos=sc.nextInt();
+        // if(pos==-1)
+        // break;
+        if(pos>c || pos<0)
+        {if(pos!=-1)
+        System.out.println("The position you entered is incorrect. Please re-enter");}
+        else
+        {
+            head=Delete(head, pos);
+            c--;
+            if(head!=null)
+            printList(head);
+        }
+        if(c==0)
+        {
+            System.out.println("All the elements have been deleted. If you like to add some, press 'E' or if you like to exit, press 'F'.");
+            ch=sc.next().charAt(0);
+            break;
+        }
+    }while(pos!=-1);
+    System.out.println("If you wish to enter elements, press 'E' else press 'F' to exit.");
+    ch=sc.next().charAt(0);
+}
+
+}while(ch!='F');
+      head= reverse(head);
+      printList(head);
+}
+}
+
+