Check whether linked lists has cycle or not!

has_cycle_linked_list.py

def has_cycle(head):
    
    if head is None:
        return False
    
    begin = end = head
    
    while (begin or end or end.next):
        if end.next is None:
            return False
        if begin.next == end.next or begin == end.next.next:
            return True
        
    begin = begin.next
    end = end.next.next
    
    return False