标签：return Tree list cs61a Link 2021 True dis14 greetings
网址 https://inst.eecs.berkeley.edu/~cs61a/fa21/disc/disc14/
problem1：
就是两种情况考虑，然后加起来就好了
def paths(x, y):
"""Return a list of ways to reach y from x by repeated
incrementing or doubling.
>>> paths(3, 5)
[[3, 4, 5]]
>>> sorted(paths(3, 6))
[[3, 4, 5, 6], [3, 6]]
>>> sorted(paths(3, 9))
[[3, 4, 5, 6, 7, 8, 9], [3, 4, 8, 9], [3, 6, 7, 8, 9]]
>>> paths(3, 3) # No calls is a valid path
[[3]]
"""
if x == y:
return [[x]]
elif x > y:
return []
else:
a = paths(x + 1, y)
b = paths(x * 2, y)
return [[x] + p for p in a + b]
problem2：
def reverse(lst):
"""Reverses lst using mutation.
>>> original_list = [5, -1, 29, 0]
>>> reverse(original_list)
>>> original_list
[0, 29, -1, 5]
>>> odd_list = [42, 72, -8]
>>> reverse(odd_list)
>>> odd_list
[-8, 72, 42]
"""
"*** YOUR CODE HERE ***"
for i in range(len(lst) // 2):
temp = lst[i]
lst[i] = lst[-(i+1)]
lst[-(i+1)] = temp
problem3:
def reverse_other(t):
"""Mutates the tree such that nodes on every other (odd-depth)
level have the labels of their branches all reversed.
>>> t = Tree(1, [Tree(2), Tree(3), Tree(4)])
>>> reverse_other(t)
>>> t
Tree(1, [Tree(4), Tree(3), Tree(2)])
>>> t = Tree(1, [Tree(2, [Tree(3, [Tree(4), Tree(5)]), Tree(6, [Tree(7)])]), Tree(8)])
>>> reverse_other(t)
>>> t
Tree(1, [Tree(8, [Tree(3, [Tree(5), Tree(4)]), Tree(6, [Tree(7)])]), Tree(2)])
"""
"*** YOUR CODE HERE ***"
def help(t, flag):
if t.is_leaf():
return
if flag :
for i in range(len(t.branches) // 2):
temp = t.branches[i].label
t.branches[i].label= t.branches[-(i+1)].label
t.branches[-(i+1)].label = temp
if flag:
flag = False
else:
flag = True
for i in t.branches:
help(i, flag)
return help(t, True)
problem4:
def deep_map(f, link):
"""Return a Link with the same structure as link but with fn mapped over
its elements. If an element is an instance of a linked list, recursively
apply f inside that linked list as well.
>>> s = Link(1, Link(Link(2, Link(3)), Link(4)))
>>> print(deep_map(lambda x: x * x, s))
<1 <4 9> 16>
>>> print(s) # unchanged
<1 <2 3> 4>
>>> print(deep_map(lambda x: 2 * x, Link(s, Link(Link(Link(5))))))
<<2 <4 6> 8> <<10>>>
"""
"*** YOUR CODE HERE ***"
if link is Link.empty:
return link
if isinstance(link.first, Link):
first = deep_map(f, link.first)
else:
first = f(link.first)
return Link(first, deep_map(f, link.rest))
probelm5:
def repeated(f):
"""
>>> double = lambda x: 2 * x
>>> funcs = repeated(double)
>>> identity = next(funcs)
>>> double = next(funcs)
>>> quad = next(funcs)
>>> oct = next(funcs)
>>> quad(1)
4
>>> oct(1)
8
>>> [g(1) for _, g in
... zip(range(5), repeated(lambda x: 2 * x))]
[1, 2, 4, 8, 16]
"""
g = lambda x : x
while True:
yield g
g = (lambda g: lambda x: f(g(x)))(g)
probelm 6:
这个和lab14的question2很像
(define (nondecreaselist s)
(if (null? s)
nil
(let ((rest (nondecreaselist (cdr s)) ))
(if (or (null? (cdr s)) (> (car s) (car (cdr s))))
(cons (list (car s)) rest)
(cons (cons (car s) (car rest)) (cdr rest))
)
)
)
problem7：
import re
def greetings(message):
"""
Returns whether a string is a greeting. Greetings begin with either Hi, Hello, or
Hey (either capitalized or lowercase), and/or end with Bye (either capitalized or lowercase) optionally followed by
an exclamation point or period.
>>> greetings("Hi! Let's talk about our favorite submissions to the Scheme Art Contest")
True
>>> greetings("Hey I just figured out that when I type the Konami Code into cs61a.org, something fun happens")
True
>>> greetings("I'm going to watch the sun set from the top of the Campanile! Bye!")
True
>>> greetings("Bye Bye Birdie is one of my favorite musicals.")
False
>>> greetings("High in the hills of Berkeley lived a legendary creature. His name was Oski")
False
>>> greetings('Hi!')
True
>>> greetings("bye")
True
"""
return bool(re.search(r'((^(Hi)|(Hey)|(hello))\b)|(\b([bB]ye)[!\.]?)$', message))
problem9and10
)标签：return,Tree,list,cs61a,Link,2021,True,dis14,greetings 来源： https://www.cnblogs.com/echoT/p/16219029.html
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