LeetCode 1816. 截断句子

示例 1：
输入：s = "Hello how are you Contestant", k = 4
输出："Hello how are you"
解释：
s 中的单词为 ["Hello", "how" "are", "you", "Contestant"]
前 4 个单词为 ["Hello", "how", "are", "you"]
因此，应当返回 "Hello how are you"

示例 2：
输入：s = "What is the solution to this problem", k = 4
输出："What is the solution"
解释：
s 中的单词为 ["What", "is" "the", "solution", "to", "this", "problem"]
前 4 个单词为 ["What", "is", "the", "solution"]
因此，应当返回 "What is the solution"

示例 3：
输入：s = "chopper is not a tanuki", k = 5
输出："chopper is not a tanuki"
 
提示：
1 <= s.length <= 500
k 的取值范围是 [1,  s 中单词的数目]
s 仅由大小写英文字母和空格组成
s 中的单词之间由单个空格隔开
不存在前导或尾随空格

class Solution:
    def truncateSentence(self, s: str, k: int) -> str:
        w = s.split(' ')
        ans = ""
        for wi in w[0:k]:
            ans += wi + " "
        return ans[0:-1] # 去除最后一个空格