151. Reverse Words in a String

Given an input string s, reverse the order of the words.

A word is defined as a sequence of non-space characters. The words in s will be separated by at least one space.

Return a string of the words in reverse order concatenated by a single space.

Note that s may contain leading or trailing spaces or multiple spaces between two words. The returned string should only have a single space separating the words. Do not include any extra spaces.

 

Example 1:

Input: s = "the sky is blue"
Output: "blue is sky the"

Example 2:

Input: s = "  hello world  "
Output: "world hello"
Explanation: Your reversed string should not contain leading or trailing spaces.

Example 3:

Input: s = "a good   example"
Output: "example good a"
Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.

Example 4:

Input: s = "  Bob    Loves  Alice   "
Output: "Alice Loves Bob"

Example 5:

Input: s = "Alice does not even like bob"
Output: "bob like even not does Alice"

 

Constraints:

  • 1 <= s.length <= 104
  • s contains English letters (upper-case and lower-case), digits, and spaces ' '.
  • There is at least one word in s.

 

Follow up:

  • Could you solve it in-place with O(1) extra space?

 

Rust Solution

struct Solution;

impl Solution {
    fn reverse_words(s: String) -> String {
        s.split_whitespace().rev().collect::<Vec<&str>>().join(" ")
    }
}

#[test]
fn test() {
    let s: String = "the sky is blue".to_string();
    let res: String = "blue is sky the".to_string();
    assert_eq!(Solution::reverse_words(s), res);
}

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