add palindrome linkedlist program in java

Program's_Contributed_By_Contributors/Java_Programs/Data_structure/PalindromeLL.java

@@ -0,0 +1,127 @@
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+class LinkedListNode<T> {
+    T data;
+    LinkedListNode<T> next;
+
+    public LinkedListNode(T data) {
+        this.data = data;
+    }
+}
+
+class Solution {
+
+    public static LinkedListNode<Integer> middle(LinkedListNode<Integer> head){
+        LinkedListNode<Integer> fast=head,slow=head;
+
+        while(fast!=null && fast.next!=null){
+            slow=slow.next;
+            fast=fast.next.next;
+        }
+        return slow;
+    }
+
+    public static LinkedListNode<Integer> reverseI(LinkedListNode<Integer> head){
+
+
+        LinkedListNode<Integer>curr=head,prev=null;
+        while(curr!=null){
+            LinkedListNode<Integer> temp=curr.next;       
+            curr.next=prev;
+            prev=curr;
+            curr=temp;
+        }
+
+        return prev;
+
+    }
+
+     public static LinkedListNode<Integer> reverseR(LinkedListNode<Integer> head){
+         if(head==null || head.next==null){
+             return head;
+         }
+         LinkedListNode<Integer> newHead=reverseR(head.next);
+         LinkedListNode<Integer> headNext=head.next;
+         headNext.next=head;
+         head.next=null;
+         return newHead;
+
+
+     }
+
+	public static boolean isPalindrome(LinkedListNode<Integer> head) {
+
+        if(head==null || head.next==null){
+            return true;
+        }
+        LinkedListNode<Integer> mid=middle(head);
+        LinkedListNode<Integer> last=reverseR(mid);
+        LinkedListNode<Integer> curr=head;
+
+        while(curr!=null && last!=null){
+            if(!(curr.data.equals(last.data))){
+                return false;
+            }
+            curr=curr.next;
+            last=last.next;
+        }
+
+        return true;
+	}
+
+}
+
+public class PalindromeLL {
+
+    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+
+    public static LinkedListNode<Integer> takeInput() throws IOException {
+        LinkedListNode<Integer> head = null, tail = null;
+
+        String[] datas = br.readLine().trim().split("\\s");
+
+        int i = 0;
+        while(i < datas.length && !datas[i].equals("-1")) {
+            int data = Integer.parseInt(datas[i]);
+            LinkedListNode<Integer> newNode = new LinkedListNode<Integer>(data);
+            if(head == null) {
+                head = newNode;
+                tail = newNode;
+            }
+            else {
+                tail.next = newNode;
+                tail = newNode;
+            }
+            i += 1;
+        }
+
+        return head;
+    }
+
+    public static void print(LinkedListNode<Integer> head){
+        while(head != null) {
+            System.out.print(head.data + " ");
+            head = head.next;
+        }
+
+        System.out.println();
+    }
+
+    public static void main(String[] args) throws NumberFormatException, IOException {
+        int t = Integer.parseInt(br.readLine().trim());
+
+        while (t > 0) {
+
+            LinkedListNode<Integer> head = takeInput(); 
+
+            boolean ans = Solution.isPalindrome(head);
+            System.out.println(ans);
+
+            t -= 1;
+
+        }
+
+    }
+}