Word Break Problem

class Solution:
    def wordBreak(self, s: str, words: List[str]) -> bool:
        n=len(s)
        dp={}
        def dfs(i):
            if i>=n:return True
            if i in dp:return dp[i]
            ans=False
            for word in words:
                if len(word)>n-i+1:continue
                w=len(word)
                if s[i:i+w]==word:
                    ans=ans or dfs(i+w)
                    if ans:break
            dp[i]=ans
            return dp[i]

        return dfs(0)