Longest Common Prefix

class Solution:
    # @return a string
    def longestCommonPrefix(self, strs):
        num_items=len(strs)
        if num_items<1:
            return ""
        prefix=strs[0]
        for i in strs[1:num_items]:
            if len(prefix)>len(i):
                prefix=prefix[0:len(i)]
            min_len=min(len(i),len(prefix))
            for j in range(min_len):
                if prefix[j]!=i[j]:
                    prefix=prefix[0:j]
                    break
        return prefix

if __name__ == '__main__':
    s=Solution()
    #strs=["abd","abcd","abcf","abchrg"]
    strs=["flower","flow","flight"]
    print(s.longestCommonPrefix(strs))