14. 最长公共前缀

编写一个函数来查找字符串数组中的最长公共前缀。如果不存在公共前缀，返回空字符串 ““。

示例：

输入1:

["flower","flow","flight"]  

输出1:

"fl"

输入2:

["dog","racecar","car"]  

输出2:

""

解答：

def longestCommonPrefix(self, strs) -> str:
    if strs is None or strs == [] : return ""
    if len(strs) == 1 : return strs[0]
    res = ""
    minLength = len(strs[0])
    for str in strs:
        if len(str) < minLength: minLength = len(str)
    n = min(len(strs[0]),minLength)
    for i in range(n):
        flag = True
        char = strs[0][i]
        for j in range(1,len(strs)):
            if char != strs[j][i] :
                flag = False
                break
        if flag: res+=char
        else: break
    return res