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# 140. Word Break II (H)

Given a string `s` and a dictionary of strings `wordDict`, add spaces in `s` to construct a sentence where each word is a valid dictionary word. Return all such possible sentences in **any order**.

**Note** that the same word in the dictionary may be reused multiple times in the segmentation.

**Example 1:**

```
Input: s = "catsanddog", wordDict = ["cat","cats","and","sand","dog"]
Output: ["cats and dog","cat sand dog"]
```

**Example 2:**

```
Input: s = "pineapplepenapple", wordDict = ["apple","pen","applepen","pine","pineapple"]
Output: ["pine apple pen apple","pineapple pen apple","pine applepen apple"]
Explanation: Note that you are allowed to reuse a dictionary word.
```

**Example 3:**

```
Input: s = "catsandog", wordDict = ["cats","dog","sand","and","cat"]
Output: []
```

**Constraints:**

* `1 <= s.length <= 20`
* `1 <= wordDict.length <= 1000`
* `1 <= wordDict[i].length <= 10`
* `s` and `wordDict[i]` consist of only lowercase English letters.
* All the strings of `wordDict` are **unique**.

### Solution: