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:
lettershas a length in range[2, 10000].lettersconsists of lowercase letters, and contains at least 2 unique letters.targetis a lowercase letter.
二分查找，找到大于给定目标的列表中最小的元素。
C++(19ms):
1 class Solution { 2 public: 3 char nextGreatestLetter(vector<char>& letters, char target) { 4 int left = 0 ; 5 int right = letters.size()-1 ; 6 while(left < right){ 7 int mid = left + (right-left)/2 ; 8 if (target < letters[mid]) 9 right = mid ; 10 else 11 left = mid + 1 ; 12 } 13 if (target < letters[left]) 14 return letters[left] ; 15 else 16 return letters[0] ; 17 } 18 };