78. 最長公共字首

給k個字串，求出他們的最長公共字首(LCP)

樣例

在 "ABCD" "ABEF" 和 "ACEF" 中,  LCP 為 "A"

在 "ABCDEFG", "ABCEFG", "ABCEFA" 中, LCP 為 "ABC"

解題思路：

class Solution:
    """
    @param strs: A list of strings
    @return: The longest common prefix
    """
    def longestCommonPrefix(self, strs):
        # write your code here
        if len(strs) == 0:
            return ''
        prefix = ''
        index = 1
        while index:
            prefix = strs[0][:index]
            print(prefix)
            COUNT = 0
            for str in strs:
                if str[:index] != prefix:
                    return str[:index-1]
                if str == prefix:
                    COUNT += 1
            if COUNT == len(strs):
                return prefix
            index += 1