[LeetCode]Find Smallest Letter Greater Than Target

题目描述:

LeetCode 744. Find Smallest Letter Greater Than Target

Given a list of sorted characters letters containing only lowercase letters, and given a target letter target, find the smallest element in the list that is larger than the given target.

Letters also wrap around. For example, if the target is target = 'z' and letters = ['a', 'b'], the answer is 'a'.

Examples:

Input:
letters = ["c", "f", "j"]
target = "a"
Output: "c"

Input:
letters = ["c", "f", "j"]
target = "c"
Output: "f"

Input:
letters = ["c", "f", "j"]
target = "d"
Output: "f"

Input:
letters = ["c", "f", "j"]
target = "g"
Output: "j"

Input:
letters = ["c", "f", "j"]
target = "j"
Output: "c"

Input:
letters = ["c", "f", "j"]
target = "k"
Output: "c"

Note:

  1. letters has a length in range [2, 10000].
  2. letters consists of lowercase letters, and contains at least 2 unique letters.
  3. target is a lowercase letter.

题目大意:

给定一组有序的字母letters,从中寻找大于字母target的最小字母,(环形有序,z < a)

解题思路:

蛮力法(Brute Force)

Python代码:

class Solution(object):
    def nextGreatestLetter(self, letters, target):
        """
        :type letters: List[str]
        :type target: str
        :rtype: str
        """
        letters = set(map(ord, letters))
        for x in range(1, 27):
            candidate = ord(target) + x
            if candidate > ord('z'):
                candidate -= 26
            if candidate in letters:
                return chr(candidate)

 

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