Code example of Java string palindrome implementation

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String Palindrome

How to determine whether a string is a palindrome string? I think you should have heard of it. Our topic today is based on this
question Modified version. If the string is stored through a singly linked list, how to determine whether it is a palindrome string? Do you have any
good solutions? What is the corresponding time and space complexity?

Ideas:
1. Use fast and slow pointers to find the intermediate node
2. While finding the intermediate node, copy a reverse linked list from the beginning to the intermediate node prev
3. Compare whether the prev linked list and slow linked list are the same

Code:

package me.study.algorithm;

/**
 * public class LinkNode {
 *
 *     char val;
 *
 *     LinkNode next;
 *
 *     public LinkNode() {
 *     }
 *
 *     public LinkNode(char val) {
 *         this.val = val;
 *     }
 * }
 */
public class StringBack {


    public boolean clac(LinkNode head) {

        if (head.next == null && head.next == null){
            return true;
        }

            LinkNode prev = null;
            LinkNode slow = head;
            LinkNode fast = head;

            while (fast != null && fast.next != null) {
                fast = fast.next.next;
                LinkNode next = slow.next;
                slow.next = prev;
                prev = slow;
                slow = next;
            }


            if (fast != null) {
                slow = slow.next;
            }

            while (slow != null) {
                if (slow.val != prev.val) {
                    return false;
                }
                slow = slow.next;
                prev = prev.next;
            }

            return true;


    }
}

Best time complexity:
The best case is a single character or an empty string, the time complexity is O( 1)

Worst time complexity:
Time complexity of finding intermediate nodes is n/2
Comparing size time complexity is not until the end to compare whether they are equal, so it is n/2
phase The total time complexity is O(n)

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