151. Reverse Words in a String

Tags

• Two Pointers
• String

Link

https://leetcode.com/problems/reverse-words-in-a-string/description/?envType=study-plan-v2&envId=leetcode-75 (opens in a new tab)

Question

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.

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: If the string data type is mutable in your language, can you solve it in-place with O(1) extra space?

Answer

JavaScript

/**
 * @param {string} s
 * @return {string}
 */
var reverseWords = function (s) {
  return s
    .trim()
    .split(" ")
    .filter((w) => w !== "")
    .reverse()
    .join(" ");
  // return s.trim().split(/\s+/).reverse().join(" ");
  // return s.split(" ").filter(x => x !== '').reverse().join(" ");
};