146-14. 最长公共前缀

通过一个函数来查找数组中所有的字符串最长公共前缀。(第一个是我写的,后面有几个很经典的,看不懂请看力扣官网)
class Solution(object):
    def longestCommonPrefix1(self, strs):
        """
        :type strs: List[str]
        :rtype: str
        """
        length = len(strs)
        if not length:
            return ""
        i = 0
        prepare_str = strs[0]
        inner_length = len(min(strs, key=len))
        while i < inner_length:
            flag = True  # 判断是否发现了不一样的字符串
            for j in range(1, length):
                if strs[j][i] != prepare_str[i]:
                    flag = False
                    break
            if not flag or i + 1 > inner_length:
                break
            i += 1
        return prepare_str[:i]

    def longestCommonPrefix2(self, strs):
        """这个方法很好,先将和第二个字符串相同的留下,每次会是的subStr长度减少
        :type strs: List[str]
        :rtype: str
        """
        if len(strs) == 0:
            return ""
        strs = sorted(strs)
        subStr = strs[0]
        for i in range(1, len(strs)):
            while strs[i].find(subStr) != 0:
                subStr = subStr[:-1]
                if subStr == "":
                    return subStr
        return  subStr

    def longestCommonPrefix3(self, strs):
        """说实话看不懂
        :type strs: List[str]
        :rtype: str
        """
        def lcp(start, end):
            if start == end:
                return strs[start]

            mid = (start + end) // 2
            lcpLeft, lcpRight = lcp(start, mid), lcp(mid + 1, end)
            minLength = min(len(lcpLeft), len(lcpRight))
            for i in range(minLength):
                if lcpLeft[i] != lcpRight[i]:
                    return lcpLeft[:i]
            return lcpLeft[:minLength]

        return "" if not strs else lcp(0, len(strs) - 1)

    def longestCommonPrefix4(self, strs):
        s=""
        zip_str = zip(*strs)
        for i in zip_str:
            if len(set(i)) == 1:
                s += i[0]
            else:
                return s
        return s

    def longestCommonPrefix5(self, strs) -> str:
        if not strs:
            return ""

        length, count = len(strs[0]), len(strs)
        for i in range(length):
            c = strs[0][i]
            if any(i == len(strs[j]) or strs[j][i] != c for j in range(1, count)):
                return strs[0][:i]

        return strs[0]

    def longestCommonPrefix6(self, strs) -> str:
        def lcp(start, end):
            if start == end:
                return strs[start]
            mid = (start + end) // 2
            inner_left, inner_right = lcp(start, mid), lcp(mid + 1, end)
            min_len = min(len(inner_left), len(inner_right))
            for i in range(min_len):
                if inner_left[i] != inner_right[i]:
                    return inner_left[:i]
            return inner_left[:min_len]

        left,  right = 0, len(strs) - 1

        return "" if not strs else lcp(left, right)

    def longestCommonPrefix(self, strs) -> str:
        """二分法查找还可以这样用,很经典"""
        def is_common_prefix(length):
            str0, count = strs[0][:length], len(strs)
            return all(strs[i][:length] == str0 for i in range(1, count))

        if not strs:
            return ""

        min_length = min(len(s) for s in strs)
        low, high = 0, min_length
        while low < high:
            mid = (high - low + 1) // 2 + low
            if is_common_prefix(mid):
                low = mid
            else:
                high = mid - 1

        return strs[0][:low]


if __name__ == '__main__':
    s = Solution()
    strs = ["flower", "flow", "flight"]
    # strs = ["dog", "d","dacecar", "d"]
    # strs = [""]
    print(s.longestCommonPrefix(strs))