Time: 100ms Space: 28.7mb You can find the actual problem here.
Since this is a singly linked (each node only contains a reference to the next node and not the previous) linked-list we are going to have to use another data structure to hold the values of the nodes. In this cause I am using a list since I can easily call .Reverse() on it. Finally I am comparing the elements in the original list to the elements in the reversed list, if they are the same then we have a palindrome.
public bool IsPalindrome(ListNode head) {
List<int> orig = new List<int>();
if(head == null){
return true;
}
if(head.next == null)
{
return true;
}
while(head != null)
{
orig.Add(head.val);
if(head.next != null){
head = head.next;
} else {
//end
head = null;
}
}
List<int> reverse = new List<int>(orig);
reverse.Reverse();
if(reverse.SequenceEqual(orig)){
return true;
} else {
return false;
}
}