78.公共子串

Ldef longestCommonPrefix(self, strs):  
    # write your code here  
    if ‘‘ in strs or strs == []:  
        return ‘‘  
    s, n = ‘‘, ‘‘  
    for j in range(min([len(i) for i in strs])):  
        for i in range(len(strs)):  
            s += strs[i][j]  
        if s == s[0]*len(s):  
            n += s[0]  
        s = ‘‘  
    return n