Project 2: CS 61A Autocorrected Typing Software

Problem 1 (1 pt)

Implement?choose, which selects which paragraph the user will type. It takes a list of?paragraphs?(strings), a?select?function that returns?True?for paragraphs that can be selected, and a non-negative index?k. The?choose?function return's the?kth paragraph for which?select?returns?True. If no such paragraph exists (because?k?is too large), then?choose?returns the empty string.

问题解析：

1.注意要求返回满足select函数的第K个段落

2.超出满足select的段落数组长度，返回空字符串（''）?

def choose(paragraphs, select, k):
    """Return the Kth paragraph from PARAGRAPHS for which SELECT called on the
    paragraph returns true. If there are fewer than K such paragraphs, return
    the empty string.
    """
    # BEGIN PROBLEM 1
    "*** YOUR CODE HERE ***"
    list_paragraph=[]
    select_cot=0

    for paragraph in paragraphs:
        if select(paragraph):
            list_paragraph.append(paragraph)
            select_cot+=1
    if k>=select_cot:
        return ''
    return list_paragraph[k]
    # END PROBLEM 1T

?

Problem 2 (2 pt)

Implement?about, which takes a list of?topic?words. It returns a function which takes a paragraph and returns a boolean indicating whether that paragraph contains any of the words in?topic. The returned function can be passed to?choose?as the?select?argument.

To make this comparison accurately, you will need to ignore case (that is, assume that uppercase and lowercase letters don't change what word it is) and punctuation.

Assume that all words in the?topic?list are already lowercased and do not contain punctuation.

Hint: You may use the string utility functions in?utils.py.

?可以仔细看看utils.py.里的函数，是解决本题的关键：

1.利用lower函数将两个判断的对象均改为小写

2.利用remove_punctuation函数将paragraph里的标点去掉

3.利用split函数将paragraphy分为一个个单词

def about(topic):
    """Return a select function that returns whether a paragraph contains one
    of the words in TOPIC.

    >>> about_dogs = about(['dog', 'dogs', 'pup', 'puppy'])
    >>> choose(['Cute Dog!', 'That is a cat.', 'Nice pup!'], about_dogs, 0)
    'Cute Dog!'
    >>> choose(['Cute Dog!', 'That is a cat.', 'Nice pup.'], about_dogs, 1)
    'Nice pup.'
    """
    assert all([lower(x) == x for x in topic]), 'topics should be lowercase.'
    # BEGIN PROBLEM 2
    "*** YOUR CODE HERE ***"
    def select(paragraph):
        for topic_element in topic:
            if lower(topic_element) in split(remove_punctuation(lower(paragraph))):
                return True
        return False
    return select
    # END PROBLEM 2