0139: Word Break

Problem Statement

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

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

Example 1:

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

Example 2:

Input: s = "applepenapple", wordDict = ["apple","pen"]
Output: true
Explanation: Return true because "applepenapple" can be segmented as "apple pen apple".
Note that you are allowed to reuse a dictionary word.

Example 3:

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

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 the strings of wordDict are unique.

Code Solution

class Solution:
    def wordBreak(self, s, wordDict):
        wdict = set(wordDict)
        w_max = len(max(*wdict, key=len))
        
        @cache
        def rec(sx):
            if sx >= len(s):
                return True
            flag = False
            for ws in range(1 + w_max):
                if s[sx:sx + ws] in wdict:
                    flag = flag or rec(sx + ws)
            return flag
        
        return rec(0)