class Solution:
    def longestCommonPrefix(self , strs: List[str]) -> str:
        # write code here
        if not strs:
            return ''
        if len(strs) == 1:
            return strs[0]
        res = [i for i in strs[0]]
        idx = 0
        for i in range(1, len(strs)):
            word = strs[i]
            while idx < len(res):
                if idx > len(word)-1:
                    res = res[:idx]
                    break
                elif res[idx] != word[idx]:
                    res = res[:idx]
                    break
                elif res[idx] == word[idx]:
                    idx += 1
            idx = 0
        return ''.join(res)