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ReverseDLL.java
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ReverseDLL.java
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import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;
public class Solution {
static class DoublyLinkedListNode {
public int data;
public DoublyLinkedListNode next;
public DoublyLinkedListNode prev;
public DoublyLinkedListNode(int nodeData) {
this.data = nodeData;
this.next = null;
this.prev = null;
}
}
static class DoublyLinkedList {
public DoublyLinkedListNode head;
public DoublyLinkedListNode tail;
public DoublyLinkedList() {
this.head = null;
this.tail = null;
}
public void insertNode(int nodeData) {
DoublyLinkedListNode node = new DoublyLinkedListNode(nodeData);
if (this.head == null) {
this.head = node;
} else {
this.tail.next = node;
node.prev = this.tail;
}
this.tail = node;
}
}
public static void printDoublyLinkedList(DoublyLinkedListNode node, String sep, BufferedWriter bufferedWriter) throws IOException {
while (node != null) {
bufferedWriter.write(String.valueOf(node.data));
node = node.next;
if (node != null) {
bufferedWriter.write(sep);
}
}
}
// Complete the reverse function below.
/*
* For your reference:
*
* DoublyLinkedListNode {
* int data;
* DoublyLinkedListNode next;
* DoublyLinkedListNode prev;
* }
*
*/
static DoublyLinkedListNode reverse(DoublyLinkedListNode head) {
if(head == null || head.next == null)
return head;
DoublyLinkedListNode cur = head, prev = null, next = null;
while(cur!=null)
{
next = cur.next;
cur.next = prev;
cur.prev = next;
prev = cur;
cur = next;
}
return prev;
}
private static final Scanner scanner = new Scanner(System.in);
public static void main(String[] args) throws IOException {
BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));
int t = scanner.nextInt();
scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");
for (int tItr = 0; tItr < t; tItr++) {
DoublyLinkedList llist = new DoublyLinkedList();
int llistCount = scanner.nextInt();
scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");
for (int i = 0; i < llistCount; i++) {
int llistItem = scanner.nextInt();
scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");
llist.insertNode(llistItem);
}
DoublyLinkedListNode llist1 = reverse(llist.head);
printDoublyLinkedList(llist1, " ", bufferedWriter);
bufferedWriter.newLine();
}
bufferedWriter.close();
scanner.close();
}
}