IsListPalindrome

Given a singly linked list of integers, determine whether or not it's a palindrome.

Example

• For l = [0, 1, 0], the output should be solution(l) = true;

• For l = [1, 2, 2, 3], the output should be solution(l) = false.

Idea

Stack

Push the copy of head to stack (1,2,2,1)

Start from start of head, pop stack (the last element added to stack)

If poped element = head element, continue iteration; else, not palindrome

Code

boolean solution(ListNode<Integer> head) {
    ListNode<Integer> slow = head;
    boolean ispalin = true;
    Stack<Integer> stack = new Stack<Integer>();

    while (slow != null) {
        stack.push(slow.value);
        slow = slow.next;
    }

    while (head != null) {

        int i = stack.pop();
        if (head.value == i) {
            ispalin = true;
        }
        else {
            ispalin = false;
            break;
        }
        head = head.next;
    }
    return ispalin;
}