LeetCode Word Break II Explained

This is another one from LeetCode: https://leetcode.com/problems/word-break-ii/

Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, add spaces in s to construct a sentence where each word is a valid dictionary word. Return all such possible sentences.

Note:

• The same word in the dictionary may be reused multiple times in the segmentation.
• You may assume the dictionary does not contain duplicate words.

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

Please give this question a try before reading further.

“catsanddog” → “catsand” + “dog”

“catsand” → “cats” + “and” or “cat” + “sand”

Do you see the pattern? Let’s try another example.

Input:
s = "pineapplepenapple"
wordDict = ["apple", "pen", "applepen", "pine", "pineapple"]
Output:
[
  "pine apple pen apple",
  "pineapple pen apple",
  "pine applepen apple"
]

“pineapplepenapple” → “pineapplepen” + “apple”

“pineapplepen” → “pineapple” + “pen” or “pine” + “applepen”