Given an circular linked list, implement an algorithm which returns the node at
the beginning of the loop.
DEFINITION
Circular linked list: A (corrupt) linked list in which a nodes’s next pointer points
to an earlier node, so as to make a loop in the linked list;
EXAMPLE
Input: A -> B -> C -> D -> E -> C [the same C as earlier]
Output: C
The general way to solve a looped linked list is using 2 iterators – fastRunner & slowRunner. fastRunner goes at 2 step/time, slowRunner goes
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