# [LeetCode] Top Interview 150 Problems Solving # 151 Reverse Words in a String

# **Understanding the Problem**

A string is given with spaces. The string could be a single character or a complete sentence. It is to reverse the string by words. The spaces at the edges should be cut off.

```python
# example 1
Input: s = "the sky is blue"
Output: "blue is sky the"

# example 2
Input: s = "  the sky is blue  "
Output: "blue is sky the"
```

# **Approach**

I would first make it a list, the reverse it. Quite a simple problem it seems.

# **Solution**

I made the string a list by `split()` so it will automatically remove all the spaces and make a word list. `s_list` below will have the value `s_list = [“the”, ”sky”, ”is”, ”blue”]`. Afterwards, I reversed the list with `s_list[::-1]`. This index sorting means it will be reversed with the value `-1`. In slicing index has got the sequence as \[start:stop:step\]. When the step has a negative value, this means in a reverse order, so in our case it was to select every elements by emptying start and stop, then reverse it with `-1` to enumerate every element.

When the list is reversed, then I simply joined the list.

```python
class Solution:
    def reverseWords(self, s: str) -> str:
        s_list = s.split()
        return " ".join(s_list[::-1])
```

# **Reflection**

If I had no knowledge about the internal methods like `split()`, `join()` and slicing technique, this problem would’ve been a conundrum. Luckily my answer had the time complexity of 0ms.