leetcode 1816. Truncate Sentence（python）

描述

A sentence is a list of words that are separated by a single space with no leading or trailing spaces. Each of the words consists of only uppercase and lowercase English letters (no punctuation).

• For example, “Hello World”, “HELLO”, and “hello world hello world” are all sentences.

You are given a sentence s​​​​​​ and an integer k​​​​​​. You want to truncate s​​​​​​ such that it contains only the first k​​​​​​ words. Return s​​​​​​ after truncating it.

Example 1:

Input: s = "Hello how are you Contestant", k = 4
Output: "Hello how are you"
Explanation:
The words in s are ["Hello", "how" "are", "you", "Contestant"].
The first 4 words are ["Hello", "how", "are", "you"].
Hence, you should return "Hello how are you".

Example 2:

Input: s = "What is the solution to this problem", k = 4
Output: "What is the solution"
Explanation:
The words in s are ["What", "is" "the", "solution", "to", "this", "problem"].
The first 4 words are ["What", "is", "the", "solution"].
Hence, you should return "What is the solution".

Example 3:

Input: s = "chopper is not a tanuki", k = 5
Output: "chopper is not a tanuki"

Note:

1 <= s.length <= 500
k is in the range [1, the number of words in s].
s consist of only lowercase and uppercase English letters and spaces.
The words in s are separated by a single space.
There are no leading or trailing spaces.

解析

根据题意，就是将句子中的前 k 个单词用空格拼接起来，用内置函数也就两行代码，我这里自己直接遍历字符串，通过判断拼接得到最后的结果，这或许就是自己给自己增加难度吧。

解答

class Solution(object):
    def truncateSentence(self, s, k):
        """
        :type s: str
        :type k: int
        :rtype: str
        """
        r = ''
        index = 0
        while k and index=1 and s[index-1]==' ':
                    index += 1
                elif index>=1 and s[index-1]!=' ':
                    index += 1
                    k -= 1
                    if k>=1:
                        r += ' '
            elif s[index]!=' ':
                r += s[index]
                index += 1
        return r

运行结果

Runtime: 16 ms, faster than 80.21% of Python online submissions for Truncate Sentence.
Memory Usage: 13.6 MB, less than 41.33% of Python online submissions for Truncate Sentence.

解析

使用内置函数

解答

class Solution(object):
    def truncateSentence(self, s, k):
        """
        :type s: str
        :type k: int
        :rtype: str
        """
        words = s.split(" ")
        return " ".join(words[0:k])

运行结果

Runtime: 12 ms, faster than 96.92% of Python online submissions for Truncate Sentence.
Memory Usage: 13.3 MB, less than 93.33% of Python online submissions for Truncate Sentence.

原题链接：https://leetcode.com/problems/truncate-sentence/

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