[Swift]LeetCode151. 翻轉字符串裏的單詞 | Reverse Words in a String

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Given an input string, reverse the string word by word.

Example:  

Input: "",
Output: "".
the sky is blueblue is sky the

Note:

• A word is defined as a sequence of non-space characters.
• Input string may contain leading or trailing spaces. However, your reversed string should not contain leading or trailing spaces.
• You need to reduce multiple spaces between two words to a single space in the reversed string.

Follow up: For C programmers, try to solve it in-place in O(1) space.

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給定一個字符串，逐個翻轉字符串中的每一個單詞。

示例:  

輸入: "",
輸出: "".
the sky is blueblue is sky the

說明:

• 無空格字符構成一個單詞。
• 輸入字符串能夠在前面或者後面包含多餘的空格，可是反轉後的字符不能包括。
• 若是兩個單詞間有多餘的空格，將反轉後單詞間的空格減小到只含一個。

進階: 請選用C語言的用戶嘗試使用 O(1) 空間複雜度的原地解法。

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1 class class Solution {
2     func reverseWords(_ s: String) -> String {
3           return String(s.split(separator: " ").reversed().reduce("") { total, word in total + word + " "}.dropLast())
4     }
5 }