Find Smallest Letter Greater Than Target.cpp

class Solution {
public:
    char nextGreatestLetter(vector<char>& letters, char target) {
        int start=0,end=letters.size()-1;
        while(start<=end){
            int mid= start +(end-start)/2;
            // if(letters[mid]==target){
            //     start=mid+1;
            // }
            if(letters[mid]<=target){
                start=mid+1;
            }
            else{
                end=mid-1;
            }
        }
        if(start==letters.size()){
            return letters[0];
        }
        return letters[start];
    }
};