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dll.java
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dll.java
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import java.util.Scanner;
class dll {
class node {
int data;
node next;
node prev;
node(int data) {
this.data = data;
this.next = null;
this.prev = null;
}
}
private node head;
private node tail;
private int size;
dll() {
tail = head = null;
size = 0;
}
void insertHead(int data) {
node newNode = new node(data);
newNode.next = head;
if (head != null) {
head.prev = newNode;
} else {
tail = newNode;
}
head = newNode;
size++;
System.out.println("Inserted");
}
void insertTail(int data) {
node newNode = new node(data);
newNode.prev = tail;
if (tail != null) {
tail.next = newNode;
} else {
head = newNode;
}
tail = newNode;
size++;
System.out.println("Inserted");
}
void insertAfter(int key, int data) {
node newNode = new node(data);
node ptr = head;
while (ptr != null) {
if (ptr.data == key) {
newNode.next = ptr.next;
newNode.prev = ptr;
if (ptr.next != null) {
ptr.next.prev = newNode;
} else {
tail = newNode;
}
ptr.next = newNode;
size++;
System.out.println("Inserted");
return;
}
ptr = ptr.next;
}
System.out.println("key not found!!");
}
void deleteHead() {
if (head == null && tail == null) {
System.out.println("underflow!!");
return;
}
head = head.next;
if (head != null) {
head.prev = null;
} else {
head = tail = null;
}
System.out.println("Deleted");
size--;
}
void deleteTail() {
if (head == null && tail == null) {
System.out.println("underflow!!");
return;
}
tail = tail.prev;
if (tail != null) {
tail.next = null;
} else {
tail = head = null;
}
System.out.println("Deleted");
size--;
}
void deleteKey(int key) {
node ptr = head;
while (ptr != null) {
if (ptr.data == key) {
if (ptr.prev == null) {
head = head.next;
}
if (ptr.next != null) {
ptr.next.prev = ptr.prev;
} else {
tail = ptr.prev;
}
if (ptr.prev != null) {
ptr.prev.next = ptr.next;
}
System.out.println("Deleted");
size--;
return;
}
ptr = ptr.next;
}
System.out.println("key not found!!");
}
void display() {
if (head == null && tail == null) {
System.out.println("underflow!!");
return;
}
node ptr = head;
System.out.println("LIST:");
while (ptr != null) {
if (ptr.next != null) {
System.out.print(ptr.data + " <=> ");
} else {
System.out.print(ptr.data);
}
ptr = ptr.next;
}
System.out.println("\nhead:" + head.data);
System.out.println("tail:" + tail.data);
}
public static void main(String[] args) {
dll doll = new dll();
Scanner in = new Scanner(System.in);
int key, p = 50, data;
char ch;
while (p > 0) {
System.out.println(
"-----OPTIONS------\n1.insert at head\n2.insert at tail\n3.insert after key\n4.delete head element\n5.delete tail element\n6.delete a key\n7.display\n8.exit\nenter option:");
ch = in.next().charAt(0);
switch (ch) {
case '1':
System.out.print("\nenter element To be Inserted:");
data = in.nextInt();
doll.insertHead(data);
break;
case '2':
System.out.print("\nenter element To be Inserted:");
data = in.nextInt();
doll.insertTail(data);
break;
case '3':
System.out.print("\nenter key:");
key = in.nextInt();
System.out.print("\nenter element To be Inserted:");
data = in.nextInt();
doll.insertAfter(key, data);
break;
case '4':
doll.deleteHead();
break;
case '5':
doll.deleteTail();
break;
case '6':
System.out.print("\nenter key:");
key = in.nextInt();
doll.deleteKey(key);
break;
case '7':
doll.display();
System.out.println("size:" + doll.size);
break;
case '8':
p = 0;
break;
default:
System.out.println("invalid option!!");
}
}
}
}