1816. Truncate Sentence

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"
```

Constraints:

• `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.

1816. Truncate Sentence
``````struct Solution;

impl Solution {
fn truncate_sentence(s: String, k: i32) -> String {
let words: Vec<&str> = s.split_whitespace().take(k as usize).collect();
words.join(" ")
}
}

#[test]
fn test() {
let s = "Hello how are you Contestant".to_string();
let k = 4;
let res = "Hello how are you".to_string();
assert_eq!(Solution::truncate_sentence(s, k), res);
}
``````