leetcode:Longest Common Prefix【Python版】

1、当strs为空，直接输出“”

2、当strs中含有“”，直接输出“”

3、strs[0]的最长长度由最短公共长度l决定（code line：15）

 class Solution:
     # @return a string
     def longestCommonPrefix(self, strs):
         if strs == []:
             return ""
         for i in range(1,len(strs)):
             l1 = len(strs[0])
             l2 = len(strs[i])
             if l1>l2:
                 l = l2
             else:
                 l = l1
             if l==0:
                 return ""
             strs[0]=strs[0][0:l]
             for j in range(l):
                 if strs[0][j] != strs[i][j]:
                     strs[0] = strs[0][0:j]
                     break
         return strs[0]