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39 lines
813 B
39 lines
813 B
#! /usr/bin/env python3
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# reverse a linked list
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class LinkedList:
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def __init__(self, head, tail):
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self.head = head
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self.tail = tail
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def __repr__(self):
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return "%s%s" % (self.head, "" if self.tail is None else ",%s" % repr(self.tail))
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def cons(x, xs):
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return LinkedList(x, xs)
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xs = cons(1, cons(2, cons(3, cons(4, cons(5, None)))))
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def push(x, xs):
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prev = xs.head
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xs.head = x
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xs.tail = cons(prev, xs.tail)
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def reverseLinkedList(xs):
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current = xs.head
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rest = xs.tail
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revd = None
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while True:
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if revd is None:
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revd = cons(current, None)
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else:
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push(current, revd)
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if rest is None:
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break
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current = rest.head
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rest = rest.tail
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return revd
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print(reverseLinkedList(xs))
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