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:
letters has a length in range [, ].
letters consists of lowercase letters, and contains at least unique letters.
target is a lowercase letter.
思路：
二分查找。
char nextGreatestLetter(vector<char>& letters, char target) {
if (letters.back() <= target) return letters.front();
int low = , high = letters.size() - ;
while (low < high) {
int mid = (low + high) / ;
if (target < letters[mid]) high = mid;
else low = mid + ;
}
return letters[low];
}
参考：
https://leetcode.com/problems/find-smallest-letter-greater-than-target/discuss/110027