class Solution(object):    def longestCommonPrefix(self, strs):        """        :type strs: List[str]        :rtype: str        """        if len(strs)==0:            return ""        result=""            s_len=len(strs[0])        for l in strs:            s_len=min(s_len,len(l))            for i in range(s_len):            ch=strs[0][i]            for j in range(1,len(strs)):                if strs[j][i]!=ch:                    return result            result+=ch            return result