151. Reverse Words in a String

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string

Description

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 cases

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 $<= 10^4$
• s contains English letters (upper-case and lower-case), digits, and spaces ' '.
• There is at least one word in s.

Approach

문자열의 모든 공백을 제거하고 단어를 역순으로 출력하는 문제이다.
js의 built-in 내장함수 trim으로 앞뒤 공백을 제거하고, 정규식 /\s+/로 하나 이상의 공백을 기준으로 문자열을 나눈다음 reverse().join(" ")으로 출력하면 간단히 해결된다

Solution Code

var reverseWords = function(s) {
    return s.trim().split(/\s+/g).reverse().join(" ")
};

Complexity

• time complexity : $O(n)$
• space complexity : $O(1)$