Given the head of a singly linked list, determine whether it reads the same forwards and backwards. The optimal solution can't just compare from both ends the way an array would, since a singly linked list has no backward pointer to walk in reverse. Instead it finds the middleSlow/Fast Pointer Middle-FindingAdvance one pointer twice as fast as another. When the fast pointer reaches the end, the slow pointer is exactly at the middle — in a single pass, no length count needed. with slow and fast pointers, reverses everything from the middle onward, and then walks two pointers outward — one across the untouched front half, one across the newly-reversed back half — checking that every pair of values matches. If they all match, it's a palindrome.