Code Testcase Test Result Test Result 744. Find Smallest Letter Greater Than Target

/*
You are given an array of characters letters that is sorted in non-decreasing order, and a character target. There are at least two different characters in letters.

Return the smallest character in letters that is lexicographically greater than target. If such a character does not exist, return the first character in letters.*/

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