return k-th to last
problem
Implement an algorithm to find the kth to last element of a singly linked list
how to solve
We use two pointers slow-pointer and fast-pointer. Firstly we proceed the fast-pointer in k step. Secondly, we move them at the same pace and slow pointer will hit the end of the linked list after k length . This algorithm takes O(n) time and O(1) space.