Create palindrome-linked-list.java

palindrome-linked-list.java

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+class Solution {
+public boolean isPalindrome(ListNode head) {
+
+    //if linkedList have only one node or null return
+    if(head==null || head.next==null) return true;
+
+    //Finding the first middle element in a linkedList.
+    ListNode slow=head;
+    ListNode fast=head;
+
+    while(fast.next!=null && fast.next.next!=null){
+        fast=fast.next.next;
+        slow=slow.next;
+    }
+
+    //getting the reverse part of linkedList and connecting it.
+    slow.next=reverseLinkedList(slow.next);
+    slow=slow.next;
+
+    //checking is palindrome or not.
+    ListNode dummy=head;
+    while(slow!=null){
+        if(dummy.val!=slow.val)
+            return false;
+        slow=slow.next;
+        dummy=dummy.next;
+    }
+    return true;
+    } 
+
+     //reversing LinkedList from middle Next.
+     ListNode reverseLinkedList(ListNode head) {
+        ListNode pre=null;
+        ListNode next=null;
+        while(head!=null){
+            next=head.next;
+            head.next=pre;
+            pre=head;
+            head=next;
+        }
+        return pre;
+    }
+}