Word Break II

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**. - Input is generated in a way that the length of the answer doesn't exceed 105.