151. Reverse Words in a String

Medium
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?

解題

func reverseWords(s string) string {
words := strings.Fields(s)
res := words[len(words)- 1]
​
for i := len(words)-2; i >= 0; i-- {
res = res + " " + words[i]
}
​
return res
}