class Solution:
    # @return a string
    def longestCommonPrefix(self, strs):
        len_strs = len(strs)
        if len_strs == 0:
            return ''
        if len_strs == 1:
            return strs[0]
        lengths = [len(i) for i in strs]
        common_prefix = ''
        for i in xrange(min(lengths)):
            tmp = strs[0][i]
            for j in xrange(1,len_strs):
                if strs[j][i] != tmp:
                    return common_prefix
            common_prefix += tmp
        return common_prefix