744_Find Smallest Letter Greater Than Target.java

class Solution {
    public char nextGreatestLetter(char[] letters, char target) {
      int start = 0;
      int end = letters.length - 1;  

      while(start <= end){
          int mid = start + (end - start) / 2;
          if(target < letters[mid]){
              end = mid -1;
          }
          else{
              start = mid + 1;
          }

      }
      return  letters[start % letters.length];
    }
}