744. Find Smallest Letter Greater Than Target

Given a characters array letters that is sorted in non-decreasing order and a character target, return the smallest character in the array that is larger than target.

Note that the letters wrap around.

• For example, if target == ‘z’ and letters == [‘a’, ‘b’], the answer is ‘a’.

class Solution {
public:
    char nextGreatestLetter(vector<char>& letters, char target) {
        auto it = upper_bound(begin(letters), end(letters), target);
        if(it == end(letters)) return letters[0];
        return *it;
    }
};