# LeetCode 151. Reverse Words in a String

## Description

https://leetcode.com/problems/reverse-words-in-a-string/

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

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"
```

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`.

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

## Explanation

Reversed and build a new string.

## Python Solution

``````class Solution:
def reverseWords(self, s: str) -> str:
result = ""

words = s.split()
for i, word in enumerate(words[::-1]):
if i != 0:
result += " "
result += word

return result``````
• Time Complexity: O(N).
• Space Complexity: O(1).