Leetcode 030. 串联所有单词的子串

class Solution:
    def findSubstring(self, s: str, words: List[str]) -> List[int]:
        m = len(s)
        n = len(words[0])
        N = len(words)
        nN = n * N
        if m < nN: 
            return []
 
        res = []
 
        for i in range(m):
            if i + nN > m:
                return res
            copied = words[:]
            for j in range(N):
                x = i+j*n
                cell = s[x:x+n]
                if cell in copied:
                    copied. remove(cell)
                else:
                    break
            else:
                res. append(i)
        return res