140 - Word Break II.

Hard

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.