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# Reverse Words in a String

String Simulation

## Problem

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.

{% hint style="info" %}
For example:

```
Input: s = "the sky is blue"
Output: "blue is sky the"
```

```
Input: s = "  hello world  "
Output: "world hello"
Explanation: Your reversed string should not
contain leading or trailing spaces.
```

```
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.
```

```
Input: s = "  Bob    Loves  Alice   "
Output: "Alice Loves Bob"
```

{% endhint %}

### Thought Process

* We need to get rid of the leading and trailing spaces 

## Solution

```
class Solution:
    def reverseWords(self, s: str) -> str:
        
        n = len(s)  
        i = n-1
        res = ""
        while i >= 0:
            while i >= 0 and s[i] == " ":
                i-=1     
            if i < 0:
                break
            j = i - 1
            while j >= 0 and s[j] != " ":
                j-=1
            sub = s[j+1:i+1]
            if len(res) == 0:
                res = sub
            else:
                res = res + " " + sub
            i = j - 1
        return res
        
```

## Time Complexity

* **Time:** O(n)
* **Space:** O(1)