El programa Javascript para verificar la lista vinculada con un bucle es Palindrome o no

Javascript

<script>
// Javascript program to check if a
// linked list with loop is palindrome
// or not.
class GfG{
 
// Link list node
class Node
{
    constructor()
    {
        this.data = 0;
        this.next = null;
    }
}
 
/* Function to find loop starting node.
   loop_node --> Pointer to one of the loop
   nodes head --> Pointer to the start node
   of the linked list */
function getLoopstart(loop_node, head)
{
    var ptr1 = loop_node;
    var ptr2 = loop_node;
 
    // Count the number of nodes in
    // loop
    var k = 1, i;
    while (ptr1.next != ptr2)
    {
        ptr1 = ptr1.next;
        k++;
    }
 
    // Fix one pointer to head
    ptr1 = head;
 
    // And the other pointer to k
    // nodes after head
    ptr2 = head;
    for (i = 0; i < k; i++)
        ptr2 = ptr2.next;
 
    /* Move both pointers at the same pace,
       they will meet at loop starting node */
    while (ptr2 != ptr1)
    {
        ptr1 = ptr1.next;
        ptr2 = ptr2.next;
    }
    return ptr1;
}
 
/* This function detects and find loop
   starting node in the list */
function detectAndgetLoopstarting(head)
{
    var slow_p = head, fast_p = head,
        loop_start = null;
 
    // Start traversing list and detect loop
    while (slow_p != null && fast_p != null &&
           fast_p.next != null)
    {
        slow_p = slow_p.next;
        fast_p = fast_p.next.next;
 
         /* If slow_p and fast_p meet then find
            the loop starting node */
         if (slow_p == fast_p)
         {
             loop_start = getLoopstart(slow_p, head);
             break;
         }
    }
 
    // Return starting node of loop
    return loop_start;
}
 
// Utility function to check if a linked
// list with loop is palindrome with given
// starting point.
function isPalindromeUtil(head, loop_start)
{
    var ptr = head;
    var s =  [];
 
    // Traverse linked list until last node
    // is equal to loop_start and store the
    // elements till start in a stack
    var count = 0;
    while (ptr != loop_start ||
           count != 1)
    {
        s.push(ptr.data);
        if (ptr == loop_start)
            count = 1;
         ptr = ptr.next;
    }
    ptr = head;
    count = 0;
 
    // Traverse linked list until last
    // node is equal to loop_start second
    // time
    while (ptr != loop_start ||
           count != 1)
    {
        // Compare data of node with
        // the top of stack
        // If equal then continue
        var stk = s.pop();
        if (ptr.data == stk);               
 
        // Else return false
        else
        {
            s.push(stk);
            return false;
        }
 
        if (ptr == loop_start)
                count = 1;
            ptr = ptr.next;
    }
    // Return true if linked list is
    // palindrome
    return true;
}
     
// Function to find if linked list
// is palindrome or not
function isPalindrome(head)
{
    // Find the loop starting node
    var loop_start =
        detectAndgetLoopstarting(head);
 
    // Check if linked list is palindrome
    return isPalindromeUtil(head,
                            loop_start);
}
 
function newNode(key)
{
    var temp = new Node();
    temp.data = key;
    temp.next = null;
    return temp;
}
 
// Driver code
var head = newNode(50);
head.next = newNode(20);
head.next.next = newNode(15);
head.next.next.next = newNode(20);
head.next.next.next.next =
newNode(50);
 
// Create a loop for testing
head.next.next.next.next.next =
head.next.next;
 
if (isPalindrome(head) == true)
    document.write("Palindrome");
else
    document.write("Not Palindrome");
// This code is contributed by aashish1995
</script>