Word Break

Word Break

Given a string s and a list of strings wordDict representing a dictionary, return true if s can be segmented into a space-separated sequence of one or more dictionary words.

Note: The same word in the dictionary may be reused multiple times in the segmentation.

Examples

Example 1:

Input: s = "leetcode", wordDict = ["leet", "code"]
Output: true
Explanation: "leetcode" can be segmented as "leet code".

Example 2:

Input: s = "applepenapple", wordDict = ["apple", "pen"]
Output: true
Explanation: "applepenapple" can be segmented as "apple pen apple".
  Note that "apple" is reused.

Example 3:

Input: s = "catsandog", wordDict = ["cats", "dog", "sand", "and", "cat"]
Output: false
Explanation: No valid segmentation exists for "catsandog".

Constraints

• 1 <= s.length <= 300
• 1 <= wordDict.length <= 1000
• 1 <= wordDict[i].length <= 20
• s and wordDict[i] consist of only lowercase English letters
• All strings in wordDict are unique

Expected Complexity

• Time: O(n^2 * m) where n is the length of s and m is the average word length (for substring comparison), or O(n^2) with hashing
• Space: O(n + k) where k is the total size of the dictionary