题目简述：

Write a function to find the longest common prefix string amongst an array of strings.

解题思路：

class Solution:

    # @return a string

    def longestCommonPrefix(self, strs):

        if strs == []:

            return ''

        minl = 99999

        for i in strs:

            if len(i) < minl:

                minl = len(i)

        pre = ''

        for i in range(minl):

            t = strs[0][i]

            for j in range(1,len(strs)):

                if t != strs[j][i]:

                    return pre

            pre += t

        return pre